Crustacean in pub clean when cooked (8)
I believe the answer is:
barnacle
'crustacean' is the definition.
(barnacle is a kind of crustacean)
'pub clean when cooked' is the wordplay.
'pub' becomes 'bar' (both are drinking establishments).
'when cooked' indicates an anagram.
'clean' anagrammed gives 'nacle'.
'bar'+'nacle'='BARNACLE'
'in' is the link.
(Other definitions for barnacle that I've seen before include "Marine crustacean (attaching to rocks, ships etc.)" , "Crustacean attached to rocks" , "Crustacean that attaches to submerged surfaces" , "One that sticks" , "kind of goose" .)