Sushi roll topping (3)
I believe the answer is:
roe
'sushi roll topping' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for roe that I've seen before include "Fish eggs; small deer" , "If hard, eggs" , "Lobster's ripe ovary" , "Food from fish" , "Mass of fish's eggs" .)