Irishman wholly supporting region of Ireland (5)

I believe the answer is:

niall

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'irishman' is the definition.
(common Irish name)

'wholly supporting region of ireland' is the wordplay.
'wholly' becomes 'all' (synonyms).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'region of ireland' becomes 'ni' (I can't justify this - if you can you should believe this answer much more).
'all' put after 'ni' is 'NIALL'.

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(Another definition for niall that I've seen is " Irishman".)

I've seen this clue in The Telegraph.

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