Greek island hordes overturned (6)
I believe the answer is:
rhodes
'greek island' is the definition.
(Rhodes is a Greek island)
'hordes overturned' is the wordplay.
'overturned' is an anagram indicator.
'hordes' with letters rearranged gives 'RHODES'.
(Other definitions for rhodes that I've seen before include "Greek island, ten miles off the Turkish coast" , "Hordes go to the Greek island" , "Horsed around on the Greek island" , "Dock for undersea craft" , "She and Rod have a Greek holiday here" .)