Crossword Genius

In military terms, prime blunder by revolutionary faction (5,4)

Ross

I believe the answer is:

booby-trap

'in military terms prime' is the definition.
(both can mean to prepare a weapon or trap)

'blunder by revolutionary faction' is the wordplay.
'blunder' becomes 'boob' ('boob' can be a synonym of 'blunder'**).
'by' is a charade indicator (letters next to each other).
'revolutionary' says the letters should be written backwards.
'faction' becomes 'party'.
'party' backwards is 'ytrap'.
'boob'+'ytrap'='BOOBY-TRAP'

I've seen this clue in The Times.
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