Bargain over a price (6)
I believe the answer is:
haggle
'bargain over a price' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for haggle that I've seen before include "Bargain over price" , "Bargain over prices" , "Try to drive a bargain" , "Wrangle over price" , "Argue about price, dicker" .)