Leftovers I reused in a stew (7)
I believe the answer is:
residue
'leftovers' is the definition.
(I've seen this before)
'i reused in a stew' is the wordplay.
'in a stew' indicates an anagram.
'i'+'reused'='ireused'
'ireused' is an anagram of 'RESIDUE'.
(Other definitions for residue that I've seen before include "waste" , "Net worth of estate" , "Dire use of what is left over" , "Material left" , "Lees, dregs" .)