Related Clues:

• With 1-Across, is very important
• Terse bit of advice
• "Stop it!"
• Admonisher's word
• Lacks the skills
• Terse warning
• 'I'd advise against it'
• Parent's warning
• It's forbidden
• "Knock it off!"
• Quitter's contraction
• Mom's warning
• 'Out of the question'
• One word of advice
• Cautionary note