Drink taking in a profit (4)
I believe the answer is:
gain
'profit' is the definition.
(I know that profit can be written as gain)
'drink taking in a' is the wordplay.
'drink' becomes 'gin' (gin is a kind of drink).
'taking in' means one lot of letters goes inside another.
'gin' placed around 'a' is 'GAIN'.
(Other definitions for gain that I've seen before include "Obtain; earn" , "Advance" , "Increase; secure" , "Pick up" , "reward" .)