Pragmatic about the business of rotten performance (12)

I believe the answer is:

matteroffact

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'rotten performance' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'pragmatic about the business of' is the wordplay.
'pragmatic' becomes 'fact' (I can't justify this - if you can you should believe this answer much more).
'about' says to put letters next to each other.
'the business' becomes 'matter' (business can mean some matter or situation).
'matter'+'of'='matterof'
'fact' put after 'matterof' is 'MATTEROFFACT'.

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I've seen this clue in The Irish Times.

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