clue

Etymology

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.

noun

1. (now rare) A strand of yarn etc. as used to guide one through a labyrinth; something which points the way, a guide.
   she had even had in the past a small smug conviction that in the domestic labyrinth she always kept the clue. 1897, Henry James, What Maisie Knew
2. Information which may lead one to a certain point or conclusion.
   Give me a clue because the question is too vague.
3. An object or a kind of indication which may be used as evidence.
   The detectives were looking for some clues at the scene of the crime.
4. Insight or understanding ("to have a clue [about]" or "to have clue". See have a clue, clue stick)
   I had little clue that I was being carefully monitored by the CCTV.

verb

1. To provide with a clue.
   The crossword compiler wasn't sure how to clue the word "should".
2. To provide someone with information which he or she lacks (often used with "in" or "up").
   Smith, clue Jones in on what's been happening.
   You need to clue me what to do, I have no idea.