Definition of “clue” - Learner’s Dictionary

clue

noun [ C ] uk us /kluː/

B2 a sign or a piece of information that helps you to solve a problem or answer a question:

Police are searching the area for clues to the murder.
I can't remember who wrote it. Give me a clue.
not have a clue informal

B2 to be completely unable to guess, understand, or deal with something:

[ + question word ] I haven't a clue what you're talking about.

(Definition of “clue” from the Cambridge Learner's Dictionary © Cambridge University Press)