Butter substitute (4)
'butter substitute' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oleo that I've seen before include "Oil used in making margarine" , "Marge" , "Prefix indicating oily" , "Fatty substance" .)
'butter substitute' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for margarine that I've seen before include "F [FAT]" , "Substitute spread for butter" , "Reg and Marian make a butter substitute" , "Item of food" , "Fat-based butter substitute" .)