hard-shell clam vs hard-shell clam

hard-shell clam and hard-shell clam both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard-shell clam	Yes	No	No	No
hard-shell clam	Yes	No	No	No

hard-shell clam (noun)	hard-shell clam (noun)
an edible American clam; the heavy shells were used as money by some American Indians	an edible American clam; the heavy shells were used as money by some American Indians
Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes	Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes