Dry, missing quaffing amount of beer? (9)
I believe the answer is:
abstinent
'dry' is the definition.
(synonyms)
'missing quaffing amount of beer?' is the wordplay.
'missing' becomes 'absent' (similar in meaning).
'quaffing' means one lot of letters goes inside another (to quaff is to drink or consume).
'amount of beer?' becomes 'tin'.
'absent' enclosing 'tin' is 'ABSTINENT'.
(Other definitions for abstinent that I've seen before include "self-restraint" , "self-control" , "nowhere near the drink" , "Avoiding alcohol" , "Not indulging appetite for food or drink" .)