From Longman Dictionary of Contemporary Englishsecret serviceˌsecret ˈservice noun → the secret service
Examples from the Corpus
secret service• A secret service contact told Mark Gutteridge that Margaret Thatcher would have seen the information.• It is some one's secret service operation, of that I am sure.• I fired one frame and the secret service guy put his hand up.• The secret service, the Securitate, remained in all but name. 