Bidder's amount (5)
I believe the answer is:
offer
'bidder's amount' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for offer that I've seen before include "Provide; reduced price" , "Express willingness - present" , "Tender, volunteer" , "Bid; proposal" , "Chance to buy at reduced price?" .)