One responsible for bust-up? (9)

I believe the answer is:

brassiere

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'one responsible for bust-up?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

This is all the clue.

Can you help me to learn more?

(Other definitions for brassiere that I've seen before include "support" , "Female undergarment supporter" , "garment" .)

I've seen this clue in The Sun.

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