Possible Clues:

• Sign of person revealing information?
• Person who gossips or blabs secrets
• Revealing or indicating something, like blabbermouth
• That's a sneaky sort of relation, perhaps, to have
• It's a giveaway, what Stevenson's alter ego could be counted on to do
• Revealing something
• Revealing, like the heart in a Poe title
• Revealing story supports Swiss marksman
• Revealing story of ancient Middle Eastern mound
• Revealing some material in Times earlier now and then