If the interviewer asks such a question, it is likely that the position entails leadership duties - current or future, which will most of the time already be outlined on the job posting. As such, he/she will assume you applied to this role upon having adequately read the job posting, and that you have an interest in leadership/team management and/or some sort of leadership/team management experience.
Tell the interviewer about your leadership or team management experience, should you have any, in a professional, volunteer, or educational capacity (alternatively). Should you have none, mention that you are more than willing to gain leadership skills and would love to take on a leadership role - and why you are a good leader.
Try to provide an example related to the position/industry you applied for, as much as possible. If you cannot do so, provide any example by telling the interviewer you are positive your skills will easily be transferable.