Declamation about seafood (4)
I believe the answer is:
clam
'seafood' is the definition.
(clam is a kind of seafood)
'declamation about' is the wordplay.
'about' indicates the answer is hidden within the clue (the clue goes around or about the answer).
'CLAM' is hidden in the letters of 'declamation'.
(Other definitions for clam that I've seen before include "Tightly closed shellfish" , "Aquatic creature" , "Secretive person - mollusc" , "Edible shellfish" , "Quahog" .)