Agitated confederates lose their reason and turn traitor? (6)

I believe the answer is:

defect

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'turn traitor?' is the definition.
(thesaurus)

I can't explain the rest of the clue.

(Other definitions for defect that I've seen before include "go over to the other side" , "Lack" , "Flaw; turn traitor" , "Transfer allegiance to opposition" , "Shortcoming" .)

I've seen this clue in The Irish Times.

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