"clandestine network" is correct and usable in written English.
It is usually used to describe a hidden group or network that is operating secretly. For example, "The spy was part of a clandestine network that worked together to gather intel on the rival government."
The FFS still managed to maintain its clandestine network despite legal repression and its leader's absence.
Most migrants to the Islamic State work with smugglers and are shepherded from place to place by a clandestine network.
That also seems to be the inspiration for Urban Secrets, a clandestine network that offers secret evenings at venues across the city.
Across northern Syria, rebel weapons workshops are part of a clandestine network of primitive arms-making plants, a signature element of a militarily lopsided war.
Across northern Syria, rebel workshops like these are part of a clandestine network of primitive arms-making plants, a signature element of a militarily lopsided war.
After arriving in London in 1942, Zygielbojm used a clandestine network of contacts across occupied Poland to gather eyewitness accounts of the fate of Jews.
In the Rosenberg case, no clandestine networks were involved.
But the clandestine networks that later evaded restrictions on Asian immigration spread beyond Harlem.
Here the artist makes visible the ship's hidden infrastructure, pushing us to think about clandestine networks and systems of transmission.
Officials there had been concerned that such a step would undermine the existing directorate of operations, which oversees the agency's clandestine networks of case officers and spies.
Composed of several dozen judges, prosecutors, and law-enforcement officers from around the world, CICIG works within Guatemala's legal system to prosecute members of organized crime and dismantle clandestine networks embedded in the state.
