Crossword Genius

Certain Irish football official joining United board (11)

Ross

I believe the answer is:

irrefutable

'certain' is the definition.
(thesaurus)

'irish football official joining united board' is the wordplay.
'irish' becomes 'ir' (abbreviation).
'football official' becomes 'ref' (ref is a kind of football official).
'joining' says to put letters next to each other.
'united' becomes 'u' (**).
'board' becomes 'table' ('table' can be a synonym of 'board').
'ir'+'ref'+'u'+'table'='IRREFUTABLE'

(Another definition for irrefutable that I've seen is " Incontrovertible".)

I've seen this clue in The Telegraph.
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