Eccentric, grim, near a butter substitute (9)
I believe the answer is:
margarine
'butter substitute' is the definition.
(I've seen this in another clue)
'eccentric grim near a' is the wordplay.
'eccentric' indicates an anagram.
'grim'+'near'+'a'='grimneara'
'grimneara' anagrammed gives 'MARGARINE'.
(Other definitions for margarine that I've seen before include "Is Ma angrier at this spread?" , "Fat-based butter substitute" , "Reg and Marian make a butter substitute" , "Substitute spread for butter" , "Vegetable fat" .)