Clue

Merriam-Webster Online Dictionary
clue (noun)
1.
something that guides through an intricate procedure or maze of difficulties , specifically a piece of evidence that leads one toward the solution of a problem
2.
- idea notion had no clue what he meant
clue (verb)
transitive verb
1.
to provide with a clue
2.
to give reliable information to - clue me in on how it happened