Related Clues:

• BO advisory
• 'All seats are taken' abbr.
• BO sign
• Sign outside a hit show
• Heavenly sign for an angel?
• Hit sign letters
• Sign of a Broadway smash
• 'No seats'
• Shout from an erratic shower
• Pained reaction
• ''That smarts!''
• 'Rent' sign, say
• Response to a pinch, perhaps
• Sign of a crowd
• 'Yeow!'