What is Clear up ?
Clear up is (verb) 1. to tidy and clean a place completely The cleaners refused to clear up the mess after the office party. 2. to solve a problem In the end, we cleared up the mystery of the missing computer disk. 3. (of weather.) to improve I hope the weather clears up because we’re going on holiday tomorrow. 4. (of an illness) to get better He has been resting, but his cold still hasn’t cleared up.
source: Easier English, Student Dictionary Upper Intermediate Level