Remaining, leftover (8)
I believe the answer is:
residual
I believe this is a double definition.
'remaining' is the first definition.
(I know that remaining can be written as residual)
'leftover' is the second definition.
(I've seen this in another clue)
(Other definitions for residual that I've seen before include "Leftover - used rail (anag)" , "unused" , "Remaining at the end" , "Concerning what is left over" , "Pertaining to what is left over" .)