Sandwich, maybe with fish for show (7)
I believe the answer is:
portray
'for show' is the definition.
(I've seen this in another clue)
'sandwich maybe with fish' is the wordplay.
'sandwich maybe' becomes 'port' (Sandwich is an English port).
'with' says to put letters next to each other.
'fish' becomes 'ray' (ray is a kind of fish).
'port'+'ray'='PORTRAY'
(Other definitions for portray that I've seen before include "Act" , "Play" , "Paint a picture" , "Depict, present" , "Delineate" .)