Seafood affected one after seconds (6)
I believe the answer is:
scampi
'seafood' is the definition.
(type of seafood)
'affected one after seconds' is the wordplay.
'affected' becomes 'camp' (camp can mean exaggerated or affected).
'one' becomes 'i' (Roman numeral).
'after' means one lot of letters go next to another.
'seconds' becomes 's'.
'camp'+'i'='campi'
'campi' after 's' is 'SCAMPI'.
(Other definitions for scampi that I've seen before include "Dish of fried shrimp or prawns" , "sort of seafood" , "Prawns, usually fried" , "Prawn dish" , "Cooked Norway lobster" .)