Greed's a sin, a rector's gathered (7)
I believe the answer is:
avarice
'greed's' is the definition.
(synonyms)
'a sin a rector's gathered' is the wordplay.
'sin' becomes 'vice'.
'rector' becomes 'r'.
'gathered' indicates putting letters inside.
'a'+'r'='ar'
'vice' placed around 'ar' is 'varice'.
'a'+'varice'='AVARICE'
(Other definitions for avarice that I've seen before include "Sway, control" , "Extreme greed for wealth" , "Parsimony" , "Cupidity" , "Greed - caviare (anag)" .)