Related Clues:

• Something you shouldn't spill
• Cryptic from some clever expert, being extremely selective
• Private about to enter camp
• Hidden camp housing soldiers
• 'Shh! It's a ___!'
• Clandestine group will admit soldiers
• Confidential, private
• "Can you keep a ___?"
• Spies dry, gnarled trees by river with very frozen water
• The __ 4D; Enid Blyton's detective group
• Like some alter egos
• Content of a whisper
• Keep it!