Defraud a character shipwrecked in novel for seafood (6)
I believe the answer is:
'seafood' is the definition.
(type of seafood)
'defraud a character shipwrecked in novel' is the wordplay.
'defraud' becomes 'scam' (to scam someone is to defraud them).
'a character shipwrecked in novel' becomes 'Pi' (in the novel Life of Pi).
'for' is the link.
(Other definitions for scampi that I've seen before include "Type of seafood", "Edible crustaceans", "Fish dish, often in rings", "Shellfish", "Large prawns as food".)