Revolutionary led island to overwhelming victory (9)
I believe the answer is:
landslide
'overwhelming victory' is the definition.
(I've seen this in another clue)
'revolutionary led island' is the wordplay.
'revolutionary' is an anagram indicator.
'led'+'island'='ledisland'
'ledisland' is an anagram of 'LANDSLIDE'.
'to' is the link.
(Other definitions for landslide that I've seen before include "big majority" , "Large earth movement" , "Overwhelming election majority" , "Overwhelming election win" , "Movement at grass-roots level" .)