nine iron vs iron

nine iron and iron both are nouns.

Word	Noun	Adjective	Verb	Adverb
nine iron	Yes	No	No	No
iron	Yes	Yes	Yes	No

As nouns, iron is a hypernym of nine iron; that is, iron is a word with a broader meaning than nine iron:

nine iron (noun)	iron (noun)
an iron with considerable loft	home appliance consisting of a flat metal base that is heated and used to smooth cloth
	a golf club that has a relatively narrow metal head
	implement used to brand live stock
	a heavy ductile magnetic metallic element; is silver-white in pure form but readily rusts; used in construction and tools and armament; plays a role in the transport of oxygen by the blood

nine iron (adjective)	iron (adjective)
	extremely robust

nine iron (verb)	iron (verb)
	press and smooth with a heated iron