Australian attitude backing fabulous writer (5)
I believe the answer is:
aesop
'fabulous writer' is the definition.
(writer of fables)
'australian attitude backing' is the wordplay.
'australian' becomes 'A'.
'attitude' becomes 'pose' (I've seen this before).
'backing' shows that the letters should be reversed in order.
'pose' written backwards gives 'esop'.
'a'+'esop'='AESOP'
(Other definitions for aesop that I've seen before include "Great Greek teller of animal fables" , "satirical writer" , "So ape the writer of fables" , "Greek storyteller" , "his writings were fabulous" .)