Gun that shattered certain outer parts of Berlin (4)

I believe the answer is:

bren

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'gun' is the definition.
(Bren is an example)

I don't understand how the remainder of the clue works.

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

I've seen this clue in the Evening Standard.

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