Herring fillet (7)
I believe the answer is:
rollmop
'herring fillet' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rollmop that I've seen before include "Curled-up herring fillet" , "Fish" , "Food" , "Dish of herring fillet" , "Herring pickled in spiced vinegar" .)