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