Introduce changes in rebate (9)
I believe the answer is:
reduction
'rebate' is the definition.
(a rebate is a reduction or refund)
'introduce changes' is the wordplay.
'changes' is an anagram indicator.
'introduce' anagrammed gives 'REDUCTION'.
'in' is the link.
(Other definitions for reduction that I've seen before include "from nine to five, for example" , "Introduce (anag) - decrease" , "Lessening" , "thickened sauce?" , "Introduce by way of discount" .)