Remote land available for purchase in reserve (7)
I believe the answer is:
outback
'remote land' is the definition.
'available for purchase in reserve' is the wordplay.
'available for purchase' becomes 'out' (eg a book that's been published is out).
'in reserve' becomes 'back' (as in items 'held back').
'out'+'back'='OUTBACK'
(Other definitions for outback that I've seen before include "uninhabited area" , "remote region" , "Bush country of Australia" , "Inland area of Australia" , "Remote and sparsely populated parts of Australia" .)