Automatic weapon begins busting riots every night (4)

I believe the answer is:

bren

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'automatic weapon' is the definition.
'Bren' can be an answer for 'weapon' (Bren is an example). I am not sure about the 'automatic' bit.

'begins busting riots every night' is the wordplay.
'begins' says to take the initial letters.
The first letters of 'busting riots every night' is 'BREN'.

Can you help me to learn more?

(Other definitions for bren that I've seen before include "World War Two machine gun" , "Weapon" , "Machine-gun" , "Light machine gun (made in Brno and Enfield)" .)

I've seen this clue in the Sydney Morning Herald.

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