It's a man wandering over a part of Australia (8)
I believe the answer is:
tasmania
'part of australia' is the definition.
(I know this)
'it's a man wandering over a' is the wordplay.
'wandering' is an anagram indicator.
'over' indicates putting letters inside.
'its'+'a'+'man'='itsaman'
'itsaman' anagrammed gives 'tsmania'.
'tsmania' enclosing 'a' is 'TASMANIA'.
(Other definitions for tasmania that I've seen before include "mountainous island" , "Island state off SE Australia, capital Hobart" , "Aussie island state" , "What a relief!" , "State off 23 [VICTORIA]" .)