Study supporting Australian port (4)
I believe the answer is:
aden
'port' is the definition.
(port in Yemen)
'study supporting australian' is the wordplay.
'study' becomes 'den' (term for a study or office).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'australian' becomes 'A' (common abbreviation).
'den' put after 'a' is 'ADEN'.
(Other definitions for aden that I've seen before include "Dane in seaport of Yemen" , "Strange Dane to be in the Yemen" , "Former Br. Gulf colony" , "Yemen's chief port" , "Commercial capital of Yemen" .)