Spread for Mrs Simpson (5)
I believe the answer is:
marge
I believe this is a double definition.
'spread' is the first definition.
(I know that marge is a type of fat spread)
'mrs simpson' is the second definition.
(I've seen this in other clues)
'for' is the link.
(Other definitions for marge that I've seen before include "Butter substitute (abbr)" , "Butter-like spread" , "Lover of Homer" , "little girl?" , "limit" .)