Largest of the Dodecanese islands (6)
I believe the answer is:
'largest of the dodecanese islands' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rhodes that I've seen before include "Horsed around on the Greek island" , "Aegean island" , "Greek island - British-born South African statesman" , "Greek port" , "Shored (anag) - Greek island" .)