Supporter has isolated emperor (9)
I believe the answer is:
bonaparte
'emperor' is the definition.
(Napoleon Bonaparte)
'supporter has isolated' is the wordplay.
'supporter' becomes 'bone' (I can't explain this - if you can you should give a lot more credence to this answer).
'has' is an insertion indicator.
'isolated' becomes 'apart' (synonyms).
'bone' going around 'apart' is 'BONAPARTE'.
Can you help me to learn more?
(Other definitions for bonaparte that I've seen before include "Old leader" , "Napoleon's family name" , "Exiled emperor" , "Corsican family" , "Extremely delicate and light" .)