A dose of processed shellfish? (7)
I believe the answer is:
seafood
'shellfish?' is the definition.
(shellfish is a kind of seafood)
'a dose of processed' is the wordplay.
'processed' indicates anagramming the letters.
'a'+'dose'+'of'='adoseof'
'adoseof' with letters rearranged gives 'SEAFOOD'.
(Other definitions for seafood that I've seen before include "Edible fish, shellfish etc from the oceans" , "Eaten fish and shellfish" , "Shellfish, marine fish" , "The "surf" of a surf 'n' turf dish" , "Such as prawns, tuna" .)