The benefit from a gin? (4)
I believe the answer is:
gain
'the benefit' is the definition.
(I've seen this before)
'from a gin?' is the wordplay.
'from' is an anagram indicator (from the letters).
'a'+'gin'='agin'
'agin' is an anagram of 'GAIN'.
(Other definitions for gain that I've seen before include "Earn, profit" , "Obtain to one's advantage" , "Pick up" , "Advance" , "Win" .)