Gluttony or greed (3)
I believe the answer is:
sin
'gluttony or greed' is the definition.
(I know that gluttony is a type of deadly sin)
This is the entire clue.
(Other definitions for sin that I've seen before include "Mortal error" , "Behave badly" , "Wrongdoing" , "Mortal offence" , "Depravity" .)