clarification vs improvement

clarification and improvement both are nouns.

Word	Noun	Adjective	Verb	Adverb
clarification	Yes	No	No	No
improvement	Yes	No	No	No

As nouns, improvement is a hypernym of clarification; that is, improvement is a word with a broader meaning than clarification:

clarification (noun)	improvement (noun)
the act of removing solid particles from a liquid	the act of improving something
an interpretation that removes obstacles to understanding	a change for the better; progress in development
	a condition superior to an earlier condition