clue
n. countablen. a piece of information that helps you solve a mystery or find an answer. You use it when you are trying to understand a difficult problem or a crime.
n. a piece of evidence or information used in the detection of a crime or the solution of a mystery. Often used figuratively to describe a hint that aids in solving any complex problem.
The police found a small clue near the window.
The detective carefully examined the muddy footprints, hoping they would provide a clue to the thief's identity.
While the initial data seemed random, a subtle pattern in the sales figures provided the first clue that the marketing strategy was actually working.
Variant of clew (“a ball of thread or yarn”), from Middle English clewe, from Old English clīewen (“ball”), from Proto-West Germanic kliuwīn, from Proto-Germanic kliuwīną, klewô (“ball, bale”), from Proto-Indo-European glew- (“to amass, conglomerate; clump, ball, bale”). Sense evolution with reference to the one which the mythical Theseus used to guide him out of the Minotaur's labyrinth. More at clew.
Commonly used with the verbs 'find', 'give', or 'provide'. In informal speech, 'no clue' is a frequent idiom meaning 'no idea'.