cleaning duty; one's turn to clean
Common in school and workplace contexts where cleaning tasks are assigned on a rotating basis.
It's my turn to do the cleaning this week.
Let's make a cleaning duty roster.
掃除当番 is a specific type of 当番 (duty/turn), referring specifically to cleaning duty.
掃除 means cleaning in general, while 掃除当番 refers to the assigned turn or duty to clean.
Compound of 掃除 (cleaning) and 当番 (duty, turn).