Occupied, as a lavatory (2-3)
I believe the answer is:
in-use
'occupied as a lavatory' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for in-use that I've seen before include "Unavailable; busy" , "In employment or practice" , "Occupied" , "Currently employed" , "Being employed -- unavailable" .)