clear up is a verb meaning "make clear and (more) comprehensible". It carries 5 recorded senses.
finish a task completely
“I finally got through this homework assignment”
make free from confusion or ambiguity; make clear
“Could you clarify these remarks?”
“Clear up the question of who is at fault”
Definitions, synonyms and semantic relations for clear up come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.