The board game Cluedo whose goal is to solve the mystery of a fictitious murder.

(now rare) A strand of yarn etc. as used to guide one through a labyrinth; something which points the way, a guide.

Information which may lead one to a certain point or conclusion.

An object or a kind of indication which may be used as evidence.

Insight or understanding ("to have a clue [about]" or "to have clue". See have a clue, clue stick)

To provide with a clue.

To provide someone with information which he or she lacks (often used with "in" or "up").