Discard as useless (5)
I believe the answer is:
scrap
'discard as useless' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for scrap that I've seen before include "A little bit of a fight" , "Fragment or morsel" , "Discarded metal or slang fight" , "Small fight about a smal fragment" , "Junk; altercation" .)