Cleaners can be added as Users and then assigned to individual properties. (see Add a Cleaner)
To change a cleaner on a property go to Properties > Tariffs > Modify property > Cleaner.
You have the option of selecting no cleaner for the property, or selecting another cleaner from the drop-down list.
Once the new cleaner is selected they will be the default cleaner for all bookings on that property.
Note: This will NOT override a cleaner that has been changed at the booking level - it only changes the default cleaner.