Said yes, ignoring a deadly sin (5)
I believe the answer is:
greed
'deadly sin' is the definition.
(greed is a kind of deadly sin)
'said yes ignoring a' is the wordplay.
'said yes' becomes 'agreed' (I've seen this before).
'ignoring' is a deletion indicator.
'agreed' with 'a' taken away is 'GREED'.
(Other definitions for greed that I've seen before include "Circuit" , "Avarice, cupidity" , "Rapacious desire" , "Voracity" , "Wanting too much" .)