Related Clues:

• Flat sound?
• Cat's ''Back off!''
• Sign of hostility
• Punctured ball sound
• Sound from a mad cat
• Angry audience reaction
• Announce the villain's arrival
• Serpent's warning
• Lottery-running org.
• Old draft letters
• Cobra's caution
• Snake's comment
• Not a good reception
• Sound after a pinprick, perhaps
• Reptilian warning