Buyer's incentive (6)
I believe the answer is:
rebate
'buyer's incentive' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rebate that I've seen before include "Money back, partial refund" , "Sum paid back" , "Money paid back" , "price reduction" , "Partial refund, reduction in payment" .)