Not in to support the bush (7)
I believe the answer is:
outback
'bush' is the definition.
(I know that Outback is a type of bush)
'not in to support' is the wordplay.
'not in' becomes 'out' ('out' is the opposite to 'in').
'to support' becomes 'back' (to back is to support or endorse).
'out'+'back'='OUTBACK'
'the' acts as a link.
(Other definitions for outback that I've seen before include "Remote Australian area" , "Australian wilderness" , "Remote land in Australia" , "Bush country of Australia" , "Australian bush country" .)