Related Clues:

• Sound for attention
• "Yo!" in the library
• Tap-on-the-shoulder alternative
• It ain't exactly "Hey!"
• Sound from a test cheater, say
• Confidential warning
• 'Ahoy!'
• 'Don't tell anyone, but...'
• Hushed ''Hey!''
• Classroom nudge
• Sibilant call
• Subtle signal
• Verbal elbow?
• Subtle "Over here!"
• Start of a library volume discussion?