operative
noun(op-er-a-tive)
a person secretly employed in espionage for a government
Synonyms: intelligence agent, intelligence officer, secret agent, 
operative
adjective(op-er-a-tive)
relating to or requiring or amenable to treatment by surgery especially as opposed to medicine
Examples:
Operative dentistry. 
operative
noun(op-er-a-tive)
someone who can be employed as a detective to collect information
Synonyms: pi, private detective, private eye, private investigator, 
shamus, 
sherlock, 
 operative
adjective(op-er-a-tive)
(of e.g. a machine) performing or capable of performing
operative
adjective(op-er-a-tive)
being in force or having or exerting force
Examples:
Operative regulations. 
The major tendencies operative in the American political system. 
operative
adjective(op-er-a-tive)
effective; producing a desired effect
Examples:
The operative word.