Possible Clues:

• Sleeveless garment worn by only child, perhaps
• Just one snitch spilled the beans
• Only one to turn informer twice
• One club maybe for a bachelor?
• Chant revealed spinster or bachelor?
• Unmarried person going topless? Seemingly not!
• Make confession to admit one's acting alone
• Vest being worn by the only child in family
• Only one to give the game away more than once
• A thing on its own