Related Clues:

• 'Upside down, are at the double sounding so happy (4)'
• '17 across, perhaps, is happy, by the sound of it (4)'
• "Got milk?" plaint
• Cat cry
• Siamese response
• Advice from 82-Across?
• Each sound is a sound of contentment
• A stroke of the cat may produce it
• Sound of a contented feline
• Sound of a happy cat
• Sound of happy cat
• Sound of happy animal
• Sound of a happy mog
• Sound of cat
• 4's sound