Bolster rotten seafood (7)
I believe the answer is:
lobster
'seafood' is the definition.
(I know that lobster is a type of seafood)
'bolster rotten' is the wordplay.
'rotten' indicates anagramming the letters.
'bolster' with letters rearranged gives 'LOBSTER'.
(Other definitions for lobster that I've seen before include "Large marine crustacean" , "Lets bro have the shellfish" , "Seafood" , "Pincered crustacean, a delicacy" , "one to loft a > shellfish?" .)