Eg, shellfish (7)
I believe the answer is:
seafood
'eg shellfish' is the definition.
(shellfish is a kind of seafood)
This is all the clue.
(Other definitions for seafood that I've seen before include "Eaten fish and shellfish" , "Shellfish, marine fish" , "Such as prawns, tuna" , "The "surf" of a surf 'n' turf dish" , "Edible fish, shellfish etc from the oceans" .)