Permitted a sin (6)
I believe the answer is:
agreed
'permitted' is the definition.
'a sin' is the wordplay.
'sin' becomes 'greed' (greed is a kind of sin).
'a'+'greed'='AGREED'
(Other definitions for agreed that I've seen before include "Was consistent" , "It's a deal!" , "Okayed" , "Tallied - reconciled" , "acceptable" .)