Related Clues:

• Shrewd and clever (Var.)
• Furtive drink with lieutenant in modest surroundings
• Skulking by lift, they drop key
• It's secret still, Mum
• Swipe your old underhand
• The wallflower is, with nitre etc scattered around
• Covert probing of NHS establishments by the Guardian repeated
• During break, call back mum
• Pinch your old-fashioned secret
• Pilfer your secret
• Twice give a quiet admonition — it's confidential
• Reserved - taciturn
• Underhand
• Covert - clandestine
• Highly confidential