So I have the answers in front of me today..
I got about 2/5 done for so I'm pretty/very happy with that, although I did mull over it for a long time and completed no work.
21d - Sober, i don't understand.
16d - Purchase, the 'firm grip' part of it refers to a form of the word i was unfamiliar with I think??
Anyway i'm still trying on the same crossword haven't checked the other half's answers yet.