(baseball) the fourth position in the batting order (usually filled by the best batter on the team)
"After leading off and second, third, the cleanup hitter stepped up to bat as the fourth player in the lineup."
The act of cleaning or tidying something.
"The volunteers spent the afternoon on a cleanup to remove trash from the park."
In plain English: A cleanup is the act of tidying up and removing messes to make an area neat again.
"We need to finish the cleanup before we leave for dinner."
Usage: Use cleanup to refer specifically to the process of removing messes, such as after an event or disaster. It is often interchangeable with clean-up when emphasizing the physical labor involved in restoring order.
The word cleanup is a shortened form of the phrase clean up. It entered English as a convenient noun derived directly from the verb meaning to tidy or clear away messes.