Drink takes a profit (4)
I believe the answer is:
gain
'profit' is the definition.
('gain' can be a synonym of 'profit')
'drink takes a' is the wordplay.
'drink' becomes 'gin' (gin is a kind of drink).
'takes' is an insertion indicator.
'gin' enclosing 'a' is 'GAIN'.
(Other definitions for gain that I've seen before include "Increase; secure" , "Win" , "Earn, profit" , "Advance" , "reward" .)