Refuse to be guilty of excessive consumption (5)
I believe the answer is:
waste
'consumption' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for waste that I've seen before include "''.... not, want not''" , "Use to no purpose" , "Spend thoughtlessly or use inefficiently" , "Useless leftovers" , "Not use effectively" .)