Alternative name in Australia sometimes (5)
I believe the answer is:
alias
'alternative name' is the definition.
(I've seen this before)
'in australia sometimes' is the wordplay.
'in' indicates a hidden word.
'ALIAS' is hidden within 'australia sometimes'.
(Other definitions for alias that I've seen before include "False or assumed name" , "stage name, perhaps" , "Cabbage salad" , "it may be assumed" , "one's assumed" .)