Answer:
When solving a mystery, characters can be clever by analyzing all of the available evidences and connect them to find the truth.
Explanation:
These are the most common traits for clever characters in a mystery genre.
While other characters look a certain object or situation as normal occurrences, Clever characters often able to understand which objects or occurrences are related to the mystery that they experience.
Characters often will find several of these evidences as the story progress, (for example, in a murder mystery this can be things such as the motif of the murder, weird statements that given by the witness, etc) but only the clever ones are able to connect these evidence that eventually solve the mystery.