A professional laundry or dry cleaner (business). (This form is now interpreted as plural and usually spelled without an apostrophe, even in official usage, to justify the removal of the apostrophe. It was traditionally spelled cleaner's with an apostrophe because this is grammatically correct, as can be seen with forms such as go to the doctor's, which cannot be reinterpreted as plural.)
A substance used for cleaning, a cleaning agent.
A person whose occupation is to clean floors, windows and other things.
A device that cleans, such as the vacuum cleaner.