Comments: PAT *ḳʷaćǝ (cf. Bz. a-ḳʷáć); PAK *ḳʷác̣ǝ. In Abkh. we must suppose a dissimilative deglottalisation of the second consonant. The meaning 'meat' in Abkh. is obviously secondary (a-ž́ǝ q.v. was the original name for meat).
Different attempts to analise the AK stem as a compound (see Shagirov 1, 217 with literature) seem rather arbitrary. It is probably best to regard the root as a whole.