hard-shell clam vs clam

hard-shell clam and clam both are nouns.

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

As nouns, clam is a hypernym of hard-shell clam; that is, clam is a word with a broader meaning than hard-shell clam:

hard-shell clam: an edible American clam; the heavy shells were used as money by some American Indians
clam: burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness

As nouns, clam is a hypernym of hard-shell clam; that is, clam is a word with a broader meaning than hard-shell clam:

hard-shell clam: Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes
clam: flesh of either hard-shell or soft-shell clams

hard-shell clam (noun)	clam (noun)
an edible American clam; the heavy shells were used as money by some American Indians	burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness
Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes	flesh of either hard-shell or soft-shell clams
	a piece of paper money worth one dollar

hard-shell clam (verb)	clam (verb)
	gather clams, by digging in the sand by the ocean