Eggs on a sushi roll (3)
I believe the answer is:
roe
'eggs on a sushi roll' 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 "If hard, eggs" , "Mass of fish eggs" , "Fish eggs; small deer" , "Food from fish" , "eg Caviare" .)