nissaṭa pp. of nis + sarati
nissaraṇa Sk. niḥsaraṇa, to nis + sarati
The primary meaning of nissaṭa in AN 10.81 is explained in SN 22.46. Its Buddha-Dhamma 101:
Removing and giving up desire (chanda) and greed (rāga) for form..
feeeling... perception... mental formations... consciousness: this is
its escape (nissaraṇaṁ).
SN 22.46
As was explained in the answer quoting SN 22.85, a Buddha is not literally free from or without five aggregates. SN 22.85 describes the ending of the life of an Arahant as:
If, friend Yamaka, they were to ask you: ‘Friend Yamaka, when a
bhikkhu is an arahant, one whose taints are destroyed, what happens to
him with the breakup of the body, after death?’—being asked thus, what
would you answer?
If they were to ask me this, friend, I would answer thus: ‘Friends,
form is impermanent; what is impermanent is unsatisfactory; what is
unsatisfactory has ceased and passed away. Feeling … Perception …
Volitional formations … Consciousness is impermanent; what is
impermanent is unsatisfactory ; what is unsatisfactory has ceased and
passed away.’ Being asked thus, friend, I would answer in such a way.
SN 22.85
Also, AN 10.81 uses the phrase: "vimariyādīkatena cetasā viharatī: his mind free of limits abides". "Cetasā/citta" is the standard Pali word used in relation to liberation of mind, such as in:
They know freed mind as ‘freed mind,’
Vimuttaṁ vā cittaṁ ‘vimuttaṁ cittan’ti pajānāti.
Rather, the goal, heartwood, and final end of the spiritual life is
the unshakable freedom of heart.”
Yā ca kho ayaṁ, brāhmaṇa, akuppā cetovimutti — etadatthamidaṁ,
brāhmaṇa, brahmacariyaṁ, etaṁ sāraṁ etaṁ pariyosānan”ti.
The limitless release of the heart, and the release of the heart
through nothingness, and the release of the heart through emptiness,
and the signless release of the heart: do these things differ in both
meaning and phrasing? Or do they mean the same thing, and differ only
in the phrasing?”
“Yā cāyaṁ, āvuso, appamāṇā cetovimutti, yā ca ākiñcaññā cetovimutti, yā ca suññatā cetovimutti, yā ca animittā cetovimutti—ime dhammā nānātthā ceva nānābyañjanā ca udāhu ekatthā byañjanameva nānan”ti?
The 'citta' is not something independent of the five aggregates. If the citta was independent of the five aggregates, then in omitting 'citta' from SN 22.59 Anatta-Lakkhana Sutta, the Buddha would have indirectly declared the 'citta' to be 'self'.
Fortunately, the Pali suttas tell us the citta is conditioned from nama-rupa, namely:
The mind originates from name and form.
Nāmarūpasamudayā cittassa samudayo;
When name and form cease, the mind ends.
nāmarūpanirodhā cittassa atthaṅgamo.
SN 47.42
'Nama-rupa' is simply the aggregates:
And what, bhikkhus, is name-and-form? Feeling, perception, volition,
contact, attention: this is called name. The four great elements and
the form derived from the four great elements: this is called form.
Thus this name and this form are together called name-and-form.
SN 12.2
To avoid doubt, in suttas directly about consciousness (such as SN 22.53), it is said consciousness (vinnana) is liberated (rather than use the word 'citta'). For example:
‘Apart from form, feeling, perception and choices, I will describe the coming and going of consciousness, its passing away and reappearing, its growth, increase, and maturity.’ That is not possible.
‘ahamaññatra rūpā aññatra vedanāya aññatra saññāya aññatra saṅkhārehi viññāṇassa āgatiṁ vā gatiṁ vā cutiṁ vā upapattiṁ vā vuddhiṁ vā virūḷhiṁ vā vepullaṁ vā paññāpessāmī’ti, netaṁ ṭhānaṁ vijjati.
If a mendicant has given up greed for the form element,
Rūpadhātuyā ce, bhikkhave, bhikkhuno rāgo pahīno hoti.
the support is cut off, and there is no foundation for [lit: the establishment/attachment of] consciousness.
Rāgassa pahānā vocchijjatārammaṇaṁ patiṭṭhā viññāṇassa na hoti.
If a mendicant has given up greed for the feeling element …
Vedanādhātuyā ce, bhikkhave …
perception element …
saññādhātuyā ce, bhikkhave …
choices element …
saṅkhāradhātuyā ce, bhikkhave …
consciousness element,
viññāṇadhātuyā ce, bhikkhave, bhikkhuno rāgo pahīno hoti.
the support is cut off, and there is no foundation for consciousness.
Rāgassa pahānā vocchijjatārammaṇaṁ patiṭṭhā viññāṇassa na hoti.
Since that consciousness does not become established and does not
grow, with no power to regenerate, it is freed.
Tadappatiṭṭhitaṁ viññāṇaṁ avirūḷhaṁ anabhisaṅkhacca vimuttaṁ.
Being free, it’s stable. Being stable, it’s content. Being content,
they’re not anxious. Not being anxious, they personally become
extinguished.
Vimuttattā ṭhitaṁ. Ṭhitattā santusitaṁ. Santusitattā na paritassati.
Aparitassaṁ paccattaññeva parinibbāyati.
They understand: ‘Birth is ended, the spiritual journey has been
completed, what had to be done has been done, there is no return to
any state of existence.’”
‘Khīṇā jāti, vusitaṁ brahmacariyaṁ, kataṁ karaṇīyaṁ, nāparaṁ
itthattāyā’ti pajānātī”ti.
SN 22.53
In conclusion, liberation of mind is liberation from greed, hated & delusion. Liberation of mind is 'liberation of mind' rather than 'liberation from mind'. Therefore, a Buddha does not have an "awareness" separate from the five aggregates. "Citta/cetasa" is not separate from the aggregates; just as "mano" ("intellect") is not separate from the aggregates. SN 12.61 says:
But that which is called ‘heart’ and also ‘intellect’ and also ‘consciousness’ arises as one thing and ceases as another all day and all night.
Yañca kho etaṁ, bhikkhave, vuccati cittaṁ itipi, mano itipi, viññāṇaṁ itipi, taṁ rattiyā ca divasassa ca aññadeva uppajjati aññaṁ nirujjhati.
SN 12.61