Rebate (4,4)
'rebate' is the definition.
(I know that rebate can be written as discount)
This is all the clue.
(Other definitions for discount that I've seen before include "Disbelieve" , "Reduction in price for conduits" , "Ignore - price reduction" , "Reduction in cost" , "Do tunics attract reduction in price?" .)
(Another definition for give back that I've seen is " Return (something)".)