To make a place tidy by removing things that are not wanted or needed. I need to clear up the living room before our guests arrive.
To solve or explain something that is confusing or not understood. The detective managed to clear up the mystery surrounding the missing necklace.
To improve in weather conditions, becoming brighter or less cloudy. The weather is supposed to clear up by the afternoon, so we can go for a walk then.
To recover from an illness or infection. My cold has finally started to clear up after a week of rest.