Unavailable because engaged (8)
I believe the answer is:
occupied
'engaged' is the definition.
('occupy' can be a synonym of 'engage')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for occupied that I've seen before include "as ladies often seem to be ..." , "Busy or inhabited" , "Inhabited or engaged" , "Filled a space, time or position" , "tied up" .)