Related Clues:

• Tree, mark, is solidly rooted
• Confidential, private
• "Can you keep a ___?"
• Solid, stable
• Tree on top of mountain is unshakeable
• Company, business
• Spies dry, gnarled trees by river with very frozen water
• The __ 4D; Enid Blyton's detective group
• Mattress specification
• Like some alter egos