Use unwisely (5)
I believe the answer is:
waste
'use unwisely' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for waste that I've seen before include "Blow - rubbish" , "Atrophy" , "Use inefficiently or inappropriately" , "Not use effectively" , "Refuse, garbage, rubbish" .)