Meaning

• 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)

Meaning

• To provide with a clue.

  "The crossword compiler wasn't sure how to clue the word "should"."

• 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."