Deduction, discount (6)
I believe the answer is:
rebate
This clue is a double definition.
'deduction' is the first definition.
(thesaurus)
'discount' is the second definition.
(rebating is a kind of discounting)
(Other definitions for rebate that I've seen before include "Beater (anag) -- partial refund" , "Refund of part of the amount paid" , "Refund - discount" , "Sum paid back" , "Money back, partial refund" .)