Spoiled, sour (6)
I believe the answer is:
rancid
I believe this clue is a double definition.
'spoiled' is the first definition.
(I've seen this in another clue)
'sour' is the second definition.
(I know that sour can be written as rancid)
(Other definitions for rancid that I've seen before include "Noxious" , "Putrid" , "Sour, rotting" , "Rank, high" , "(Of butter) gone off" .)