Possible Clues:

• In which real duty is abandoned!
• Lady true about reason for divorce
• The act of being unfaithful to spouse (8)
• Extramarital sex
• Frequent subject on 'Desperate Housewives'
• A sin for grown-ups in bad faith
• Sinful act with lady, true to form
• Old enough to commit?
• Maybe where grown-ups are made frowned-on relations
• The act of marital infidelity