light up vs clear up

light up and clear up both are verbs.

Word	Noun	Adjective	Verb	Adverb
light up	No	No	Yes	No
clear up	No	No	Yes	No

As verbs, light up and clear up are synonyms defined as:

Other synonyms of light up include brighten, clear.

light up (verb)	clear up (verb)
introduce light into	free (the throat) by making a rasping sound
begin to smoke	finish a task completely
become clear	make free from confusion or ambiguity; make clear
start to burn with a bright flame	make clear and (more) comprehensible
ignite	become clear