Related Clues:

• Terse negative
• "You're dreaming"
• Slangy denial, and a hint to 20-, 29-, 46- and 56-Across
• "Not a chance"
• 'ÔFraid not'
• "Won't do it"
• 'Not gonna happen!'
• Uncouple every other one? Not on your life!
• Negative response of number needing exercise
• Lack of exercise? Not on your life!
• 'Fuhgeddaboudit'
• ''You're mistaken''
• "You wish"
• Opposite of "Yup"
• Slangy veto