Abstract algebra's used by Irish official? It's indisputable (12)

I believe the answer is:

irrefragable

'indisputable' is the definition.
(thesaurus)

'abstract algebra's used by irish official?' is the wordplay.
'abstract' is an anagram indicator.
'used by' is a charade indicator (letters next to each other).
'irish' becomes 'ir' (abbreviation).
'official?' becomes 'ref' (match official in football, say).
'algebra' is an anagram of 'ragable'.
'ir'+'ref'='irref'
'ragable' put after 'irref' is 'IRREFRAGABLE'.

'it's' is the link.

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.