Related Clues:

• Moral misdeed
• It's outlawed
• Trig function
• Subside
• Trig ratio
• No-no
• Come to an end
• Expire
• 'That's a ___!'
• Talking during a film, e.g.
• First mistake
• Avarice, e.g.
• Thou-shalt-not
• Major no-no
• Forbidden fruit