What is "Clandestine"?

Another newsreader -- male this time -- just regaled us with details of a "clandestine" drug lab in Mandurah.
The origin of this word is Latin: clam.
As in "to clam up"?
What was the poor bugger supposed to do?
Stick his drug lab in the main street (do they have one?) with a great big neon sign saying "DRUGS HERE"?