It sounds a beastly form of warfare (9)

I believe the answer is:

guerrilla

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'it sounds a beastly form of warfare' is the definition.
The definition suggests a singular noun which matches the answer.

This is all the clue.

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(Other definitions for guerrilla that I've seen before include "Resistance fighter" , "Combatant" , "in conflict to secure political end?" , "Irregular bandit" , "political insurgent" .)

I've seen this clue in The Globe and Mail.

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