Piece of bread, possibly to follow the fish (5)
I believe the answer is:
slice
'piece of bread' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for slice that I've seen before include "Piece (of cake?)" , "Piece cut from a larger portion" , "Spin" , "Portion of pizza" , "Cut into portions" .)