Greed, a weakness holding painter back (7)
I believe the answer is:
avarice
'greed' is the definition.
(avarice is a kind of greed)
'a weakness holding painter back' is the wordplay.
'weakness' becomes 'vice' (I've seen this before).
'holding' means one lot of letters goes inside another.
'painter' becomes 'ra'.
'back' shows that the letters should be reversed in order.
'ra' back-to-front is 'ar'.
'vice' going around 'ar' is 'varice'.
'a'+'varice'='AVARICE'
(Other definitions for avarice that I've seen before include "Insatiable lust" , "Greed, covetousness" , "excessive desire for wealth" , "Rapacity" , "Greed for gain" .)