Degenerate bum stealing pounds (9)
I believe the answer is:
backslide
'degenerate' is the definition.
(backslide can mean to relapse or degenerate)
'bum stealing pounds' is the wordplay.
I cannot really understand how this works, but
'pounds' could be 'l' (abbreviation e.g. Lsd - pounds, shillings, pence) and 'l' is found in the answer.
'bum' could be 'backside' (synonyms) and 'backside' is found in the remaining letters.
No letters remain.
This explanation may well be incorrect...
(Other definitions for backslide that I've seen before include "Degenerate" , "Relapse into bad ways" , "Lapse into bad habits" .)