Greed is a moral weakness consuming upstanding artist (7)
I believe the answer is:
avarice
'greed' is the definition.
(synonyms)
'a moral weakness consuming upstanding artist' is the wordplay.
'moral weakness' becomes 'vice' (I've seen this in another clue).
'consuming' means one lot of letters goes inside another.
'upstanding' says the letters should be written backwards.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'ra' back-to-front is 'ar'.
'vice' going around 'ar' is 'varice'.
'a'+'varice'='AVARICE'
'is' acts as a link.
(Other definitions for avarice that I've seen before include "Wanting to be rich" , "Rapacity" , "Extreme greed for wealth" , "Insatiable lust" , "Parsimony" .)