Or brute poses a problem, being unruly (12)

I believe the answer is:

obstreperous

'being unruly' is the definition.
('obstreperous' can be a synonym of 'unruly')

'or brute poses a problem' is the wordplay.
'a problem' indicates anagramming the letters.
'or'+'brute'+'poses'='orbruteposes'
'orbruteposes' with letters rearranged gives 'OBSTREPEROUS'.

(Other definitions for obstreperous that I've seen before include "Noisily aggressive" , "Bolshie" , "Noisily defiant" , "Sober posture (anag) - unruly" , "Disruptive" .)

I've seen this clue in The Irish Independent.

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