Sushi roll topper (3)
I believe the answer is:
roe
'sushi roll topper' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roe that I've seen before include "Lobster's ripe ovary" , "Food from fish" , "eg Caviare" , "Caviar" , "Mass of fish's eggs" .)