provocateur
noun /prəˌvɒkəˈtɜː(r)/
/prəˌvɑːkəˈtɜːr/
(also agent provocateur)
(from French)- a person who is employed by a government to encourage people in political groups to do something illegal so that they can be arrested
(受雇于政府,怂恿某些政治团体人士犯法以便将之逮捕的)密探,坐探