Australia has singular, bracing air (5)
I believe the answer is:
ozone
'bracing air' is the definition.
(I've seen this before)
'australia has singular' is the wordplay.
'australia' becomes 'oz'.
'has' is a charade indicator (letters next to each other).
'singular' becomes 'one' ('one' can be a synonym of 'singular').
'oz'+'one'='OZONE'
(Other definitions for ozone that I've seen before include "(Depleted) layer of gas" , "Allotrope of oxygen" , "Layer that protects against ultraviolet rays" , "Toxic form of oxygen" , "Sea air; bleaching agent" .)