Butter or margarine, eg (6)
I believe the answer is:
spread
This clue is a double definition.
'butter' is the first definition.
(thesaurus)
'margarine eg' is the second definition.
(margarine is a kind of spread)
(Other definitions for spread that I've seen before include "Land in America" , "expansion?" , "Extend - banquet" , "Disseminate through padres" , "Broaden - drapes (anag)" .)