Sydney citizen (6)
I believe the answer is:
aussie
'sydney citizen' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aussie that I've seen before include "Antipodean native, informally" , "Someone from Melbourne, perhaps (slang)" , "could be Victorian" , "Australian (colloq.)" , "Digger" .)