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