Not in favour of a drink with tonic? (4)
I believe the answer is:
agin
'not in favour of' is the definition.
(I've seen this before)
'a drink with tonic?' is the wordplay.
'drink with tonic?' becomes 'gin' (drink often mixed with tonic).
'a'+'gin'='AGIN'
(Other definitions for agin that I've seen before include "Hostile to" , "Dialect form of against" , "Not a fan of" , "Not in favour of" , "Against (facetious)" .)