Amount left over (7)
I believe the answer is:
surplus
This clue is a triple definition!
'amount' is the first definition.
(surplus is a kind of amount)
'left' is the second definition.
(thesaurus)
'over' is the third definition.
(thesaurus)
(Other definitions for surplus that I've seen before include "Superabundance" , "Surfeit" , "Amount left over" , "a bit over the top" , "balance" .)