Dieting, he eschewed some butter (4)
I believe the answer is:
ghee
'butter' is the definition.
(I know that ghee is a type of clarified butter)
'dieting he eschewed some' is the wordplay.
'some' says the answer is hidden in the clue.
'GHEE' is hidden in the letters of 'dieting he eschewed'.
(Other definitions for ghee that I've seen before include "Clarified butter used in Indian cookery" , "type of butter" , "Indian form of butter" , "Clarified butter used in Indian cooking" , "Use it to cook" .)