Related Clues:

• Fingerprint or dropped handkerchief, say
• Heater
• This, for example
• Detective's need
• Gat
• Print, maybe
• Work of art
• It may be found with a magnifying glass
• Guiding light?
• Inkling
• Fingerprint, perhaps
• See 68-Down
• Musical work
• Sleuth's find
• Bishop, e.g.