Man hides recipe for shellfish (5)
I believe the answer is:
prawn
'shellfish' is the definition.
(thesaurus)
'man hides recipe' is the wordplay.
'man' becomes 'pawn' (pawn is a kind of man**).
'hides' indicates putting letters inside.
'recipe' becomes 'r' (abbreviation).
'pawn' enclosing 'r' is 'PRAWN'.
'for' is the link.
(Other definitions for prawn that I've seen before include "Large shrimp" , "Small, edible crustacean" , "Cocktail ingredient" , "Shellfish" , "Cocktail item" .)