clue

now rareA 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.

“Give me a clue because the question is too vague.”

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.”

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.”

Evidence that helps to solve a problem

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.”

“You need to clue me what to do, I have no idea.”

Roll into a ball