Empty pan containing uncooked shellfish (5)
I believe the answer is:
prawn
'shellfish' is the definition.
(I've seen this before)
'empty pan containing uncooked' is the wordplay.
'empty' means to remove the middle letters.
'containing' means one lot of letters goes inside another.
'uncooked' becomes 'raw' (similar in meaning).
'pan' with its centre removed is 'pn'.
'pn' enclosing 'raw' is 'PRAWN'.
(Other definitions for prawn that I've seen before include "Marine crustacean" , "Bit of seafood" , "Small tasty crustacean, nice in cocktail" , "Popular oriental snack" , "Shrimp-like crustacean" .)