Maybe oligarch’s rage after charge for possessing island (11)
I believe the answer is:
billionaire
'maybe oligarch's' is the definition.
I can't judge whether this defines the answer.
'rage after charge for possessing island' is the wordplay.
I cannot really see how this works, but
'rage' could be 'ire' (ire is anger) and 'ire' is located in the answer.
'charge' could be 'bill' (synonyms) and 'bill' is present in the answer.
'island' could be 'iona' (Scottish island) and 'iona' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for billionaire that I've seen is " Very rich person".)