Though a change of address is unavailable, vacate (4,3)
I believe the answer is:
move out
'vacate' is the definition.
(I've seen this in another clue)
'though a change of address is unavailable' is the wordplay.
I cannot really see how this works, but
'change' could be 'move' (move is a kind of change) and 'move' is present in the answer.
'of' could be 'o' and 'o' is located in the answer.
The remaining letters 'ut' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for move out that I've seen before include "Perhaps leave one's castle forever" , "Vacate premises" , "Leave home" .)