Disturbed purist accepts it will cause trouble (4,2,2)

I believe the answer is:

stir it up

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

'disturbed purist accepts it' is the wordplay.
'disturbed' is an anagram indicator (the order of letters is disturbed).
'accepts' indicates putting letters inside.
'purist' is an anagram of 'stirup'.
'stirup' enclosing 'it' is 'STIR IT UP'.

'will' is the link.

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I've seen this clue in The Irish Times.

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