Broom of magical cleaning is enchanted magical item. Creating it follows normal rules and is 1st level Magic-User spell. Broom is activated like normal magic item and starts to clean up the place. But no one has yet completed the spell to be reliable. Roll 1d8 to see how broom works that time:
1 - 2 Nothing happens
3 - 5 Broom cleans but leaves spots
6 - Broom cleans perfectly
7 - 8 Broom destroys places and makes worse mess!
(Rules for magic items staffs for example from LotFP or other OSR/clone/d20 games or game system of your choice.)