Money we got back for nut (6)
I believe the answer is:
cashew
'for nut' is the definition.
(cashew is a kind of nut)
'money we got back' is the wordplay.
'money' becomes 'cash' (cash is a type of money).
'got back' shows that the letters should be reversed in order.
'we' backwards is 'ew'.
'cash'+'ew'='CASHEW'
(Other definitions for cashew that I've seen before include "snack perhaps" , "Acajou" , "nut-tree" , "Chew as you would this nut" , "Kidney-shaped nut of tropical tree" .)