Invoice topping island anger — who could afford it? (11)

I believe the answer is:

billionaire

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'invoice topping island anger who could afford it?' is the definition.
The definition suggests a singular noun which matches the answer.

'invoice topping island anger' is the wordplay.
'invoice' becomes 'bill' (synonyms).
'topping island' becomes 'iona' (Scottish island. I am not sure about the 'topping' bit.).
'anger' becomes 'ire' (ire is intense rage).
'bill'+'iona'+'ire'='BILLIONAIRE'

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(Another definition for billionaire that I've seen is " Very rich person".)

I've seen this clue in The Times.

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