таємний (також - нелегальний); суворо засекречений (про розвідку / термін спецслужб)
clandestine operation; covert operation
clandestine border crossing
clandestine operation
clandestine organization
experience with clandestine work
keeper of a clandestine address
give clandestine assistance
clandestine agencies
clandestine agent
clandestine assembly area
clandestine force
clandestine operations
clandestine passive resistance
clandestine patrol base
clandestine reconnaissance
clandestine warfare