Sloth, for one (6,3)
I believe the answer is:
deadly sin
'sloth for one' is the definition.
(sloth is a kind of deadly sin)
This is the entire clue.
(Other definitions for deadly sin that I've seen before include "It's one of seven, gluttony say" , "Eg, lust or gluttony" , "greed, or lust" , "a cause of damnation" , "Greed, perhaps" .)