A south-west state and a north-east state backing midland Australia (7)
I believe the answer is:
arizona
'a south-west state' is the definition.
'a north-east state backing midland australia' is the wordplay.
'north-east state' becomes 'ri' (Rhode Island American state).
'backing' says the letters should be written in reverse.
'midland' becomes 'an' (the middle of 'land').
'australia' becomes 'oz'.
'an'+'oz'='anoz'
'anoz' reversed gives 'zona'.
'a'+'ri'+'zona'='ARIZONA'
'and' is the link.
(Other definitions for arizona that I've seen before include "State of south-western US" , "State of southern US" , "State in south-west US" , "Western US state" , "Site of Grand Canyon" .)