Fight waste (5)
I believe the answer is:
scrap
This clue is a double definition.
'fight' is the first definition.
(a scrap is a minor fight)
'waste' is the second definition.
(I know that scrap is a type of waste)
(Other definitions for scrap that I've seen before include "Small piece; abolish" , "Discarded metal or slang fight" , "A fragment or an informal fight" , "Leftover; fight" , "Dispense with - waste material" .)