Answer:

shellfish

Answer	Crossword Clue
SHELLFISH	Clams and oysters
SHELLFISH	Clams and crabs
SHELLFISH	Scallop.

SHELLFISH	What an underwater gunner can do
SHELLFISH	Mollusks
SHELLFISH	Nonkosher food
SHELLFISH	Oyster, e.g.
SHELLFISH	Mollusk or crustacean
SHELLFISH	Cause of some allergic reactions
SHELLFISH	What some are allergic to