Backing for singer during quiet drink? That's OK (8)
I believe the answer is:
passable
'ok' is the definition.
(thesaurus)
'backing for singer during quiet drink?' is the wordplay.
'backing for' is a reversal indicator.
'singer' becomes 'bass' (bass is a kind of singer).
'during' is an insertion indicator.
'quiet' becomes 'p' (music symbol for 'piano').
'drink?' becomes 'ale' (ale is a kind of drink).
'bass' back-to-front is 'ssab'.
'p'+'ale'='pale'
'ssab' placed within 'pale' is 'PASSABLE'.
'that's' acts as a link.
(Other definitions for passable that I've seen before include "examinations should be!" , "Good enough to be acceptable" , "OK" , "okay?" , "not hogging the road" .)