Sauce or garnish for food (7)
I believe the answer is:
topping
This clue is a double definition.
'sauce' is the first definition.
(sauce is a type of topping)
'garnish for food' is the second definition.
(I've seen this before)
(Other definitions for topping that I've seen before include "garnish for food" , "Polishing off" , "Sauce; excellent (dated)" , "Garnish - splendid!" , "Absolutely excellent!" .)