Related Clues:

• Word after book or street
• Not open
• Very perceptive
• Shrewdly cautious
• __ as a tack
• Like crossword puzzle solvers
• Sting some
• Like a useful knife
• Pitched too high
• Like some observations
• Off-key, perhaps
• Shrewd or savvy
• Mensa-eligible
• Mentally blessed
• Shrewd (Var.)