A more thorough explanation:

Definition: To force or pressure someone to do something.

Example 1: The police can compel a suspect to come to the station for questioning.

Example 2: The judge can compel a witness to testify in court.

Explanation: In both examples, someone is being forced or pressured to do something they may not want to do. The police can use their authority to make a suspect come to the station, and the judge can use their power to make a witness testify. This is what it means to compel someone.