Radical Aussie in the main fully backs islands (6)
I believe the answer is:
azores
'islands' is the definition.
(I know that Azores is a islands)
'radical aussie in the main fully backs' is the wordplay.
I cannot really understand how this works, but
'radical' could be 'azo' (azo radical is a kind of radical) and 'azo' is found in the answer.
The remaining letters 'res' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for azores that I've seen before include "Three groups of North Atlantic volcanic islands" , "Group of islands in the middle of the north Atlantic" , "Islands in the Atlantic Ocean" , "Portuguese archipelago" , "isolated set" .)