agent provocateur      
noun [ C ] uk/ˌæʒ.ɑ̃ː prəˌvɒk.əˈtɜːr/ us/ˌɑːʒ.ɑ̃ː proʊˌvɑː.kəˈtɝː/  agents provocateurs uk/ˌæʒ.ɑ̃ː.prəˌvɒk.əˈtɜːr/ us/ˌɑːʒ.ɑ̃ː.proʊˌvɑː.kəˈtɝː/
 (诱使反政府人士违法以便将之抓捕的)密探,坐探
a person who intentionally encourages people to do something illegal so that they can be caught