The beasts who bashed up Buster (6)

I believe the answer is:

brutes

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'the beasts who bashed' is the definition.
'brutes' can be an answer for 'the beasts' ('brute' can be a synonym of 'beast'). I am not certain of the remainder of the definition.

'up buster' is the wordplay.
'up' is an anagram indicator (letters get chucked up).
'buster' is an anagram of 'BRUTES'.

Can you help me to learn more?

(Other definitions for brutes that I've seen before include "Beasts" , "Animals other than humans (6)" , "Savages" , "Savagely violent men or animals" .)

I've seen this clue in the Evening Standard.

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