Modern Midas touched a senior, one enthralling old writer (13)

I believe the answer is:

squillionaire

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'modern midas' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'touched a senior one enthralling old writer' is the wordplay.
'touched' is an anagram indicator (letters touched or moved about).
'one' becomes 'i' (Roman numeral).
'enthralling' indicates putting letters inside.
'old writer' becomes 'quill' (historical writing implement).
'a'+'senior'+'i'='aseniori'
'aseniori' is an anagram of 'sionaire'.
'sionaire' enclosing 'quill' is 'SQUILLIONAIRE'.

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I've seen this clue in the Sydney Morning Herald.

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