Secretive org. (3)
(Another definition for nsa that I've seen is " US monitoring agency".)
(Other definitions for fbi that I've seen before include "J. Edgar Hoover long its director" , "J. Edgar Hoover's organisation" , "Initially, J Edgar Hoover's law force" , "law enforcers" , "US law enforcement agency" .)
(Other definitions for cia that I've seen before include "Secret service agency of USA" , "Famous American intelligence agency, advises President" , "US spy bureau" , "US intelligence organisation" , "US investigative organisation" .)