Coup d'état (6)
I believe the answer is:
putsch
'coup d'etat' is the definition.
(synonyms)
This is all the clue.
(Other definitions for putsch that I've seen before include "Violent attempt to overthrow a government" , "Change of government by force" , "Coup d'etat" , "Coup dtat" , "A sudden political rebellion" .)