The antonyms for the word "cleans it up" can be "dirtying it", "messing it up", or "making it messy". These words describe the opposite action of cleaning up something, which is to make it untidy, soiled or disorganized. When we say that someone has "cleaned it up", we usually mean that they have made something neat, tidy, and clean. In contrast, when we say that someone has "messed it up" or "made it dirty", we imply that they have created a mess or made something unclean. The antonyms of "cleans it up" can be useful when we want to describe situations where someone has made something worse instead of better.