Gross or net gain (6)
I believe the answer is:
profit
This clue is a double definition.
'gross' is the first definition.
(thesaurus)
'net gain' is the second definition.
(I've seen this before)
(Other definitions for profit that I've seen before include "It's gained on a transaction" , "Financial gain" , "bonus" , "Use" , "Gain from employment of capital" .)