one iron vs driving iron

one iron and driving iron both are nouns.

Word	Noun	Adjective	Verb	Adverb
one iron	Yes	No	No	No
driving iron	Yes	No	No	No

As nouns, one iron and driving iron are synonyms defined as:

one iron and driving iron: (golf) the long iron with the most nearly vertical face

one iron (noun)	driving iron (noun)
(golf) the long iron with the most nearly vertical face	(golf) the long iron with the most nearly vertical face