Remaining, surplus (8)
I believe the answer is:
I believe this clue is a double definition.
'remaining' is the first definition.
(I know that remaining can be written as leftover)
'surplus' is the second definition.
(Other definitions for leftover that I've seen before include "something you'd keep on the plate!" , "Remaining" , "What remains" , "Remnant" , "Finally unused" .)