Related Clues:

• Mum's the word
• Audience utterance
• "Pipe down!"
• Stunned response
• Stillness
• Gag
• Teacher's command
• Cry hidden seven times elsewhere in this puzzle
• "Quiet!"
• Hush
• Theater request
• 'Quiet down!'
• 'Zip it!'
• "Hush!"
• Librarian's plea