Related Clues:

• Author's kiss of death
• Legal prohibition
• Unwise act
• Secret rival?
• Double denial
• *Like secret military facilities, to civilians
• Out-of-bounds
• Injunction
• Thing to avoid
• Put an embargo on
• Burping in public, e.g.
• Ill-advised move
• Off-limits act
• It just isn't done
• Non-starter