The phrase "a key operative" is correct and usable in written English.
It can be used to refer to an important or essential person involved in a particular operation or activity, often in a business or organizational context.
Example: "She was recognized as a key operative in the successful launch of the new marketing campaign."
Alternatives: "a crucial player" or "an essential member".
A federal prosecutor, speaking in United States District Court in Brooklyn on Friday, disclosed what he said was the role of the two senior Qaeda leaders for the first time and identified them as Saleh al-Somali, the group's head of external operations, and Rashid Rauf, a key operative.
Both men have been cooperating with the office of the United States attorney in Brooklyn and the Federal Bureau of Investigation, and prosecutors have said in court that they met with two senior Qaeda leaders in Pakistan, Saleh al-Somali, the group's head of external operations, and Rashid Rauf, a key operative, who sent the men back to New York to carry out a suicide strike.
Sydney Howard Gay was the editor of the weekly abolitionist publication, the National Anti-Slavery Standard and a key operative in the underground railroad in New York City.
"Design" is a key, operative word: urban designers design urban physical environments both directly through the design of actual projects and indirectly through plans.
Police officers played down reports Aswat was a key operative in the London plots, though he is alleged to be connected to an investigation by US authorities into supposed attempts to set up training camps in Oregon in 1999.
In 1855 and 1856, Sydney Howard Gay, a key operative in the underground railroad in New York City, decided for unknown reasons to meticulously record the arrival of fugitive slaves at his office.
While DaimlerChrysler's board has met regularly in New York, and some key employees have had offices here, Mr. Schrempp is said to believe that a move to the Chrysler Building, even by a few key operatives, could represent a powerful signal that a company with global ambitions was ready to play in New York.
"We are never going to win most of these states until we can do something about those unions," one key operative said at a Washington dinner in November.
The new U.S. Expeditionary Targeting Force in Iraq — led by some fifty Delta Force commandos — has scored the first capture of a key ISIS operative, the Pentagon said on Tuesday.
Mr. Hindi was described by a senior government official as "a key Al Qaeda operative in Great Britain," and was said to have been under surveillance by British authorities even before the computer files were discovered last week.
A key security operative of the Palestinian Islamist movement Hamas was under arrest in Syria tonight on suspicion of having helped an alleged Israeli hit squad identify Mahmoud al-Mabhouh before he was assassinated in Dubai, the Guardian has learned.
