rustiness vs clumsiness

rustiness and clumsiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
rustiness	Yes	No	No	No
clumsiness	Yes	No	No	No

As nouns, clumsiness is a hypernym of rustiness; that is, clumsiness is a word with a broader meaning than rustiness:

rustiness: ineptitude or awkwardness as a consequence of age or lack of practice
clumsiness: unskillfulness resulting from a lack of training

Other hypernyms of rustiness include awkwardness, ineptitude, ineptness, maladroitness, slowness.

rustiness (noun)	clumsiness (noun)
ineptitude or awkwardness as a consequence of age or lack of practice	the carriage of someone whose movements and posture are ungainly or inelegant
the condition of being coated or clogged with rust	the inelegance of someone stiff and unrelaxed (as by embarrassment)
	unskillfulness resulting from a lack of training