Seafood not cooked at noon following pressure (5)
I believe the answer is:
prawn
'seafood' is the definition.
(I know that prawn is a type of seafood)
'not cooked at noon following pressure' is the wordplay.
'not cooked' becomes 'raw' ('raw' is the opposite to 'cooked').
'at' means one lot of letters go next to another.
'noon' becomes 'n' (abbreviation).
'following' is a charade indicator (letters next to each other).
'pressure' becomes 'p' (scientific abbreviation).
'raw' put next to 'n' is 'rawn'.
'rawn' after 'p' is 'PRAWN'.
(Other definitions for prawn that I've seen before include "Shellfish" , "Shrimp-like crustacean" , "Cocktail ingredient" , "Cocktail item" , "Popular oriental snack" .)