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.
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.
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.
"I lead a team of individuals in a volunteer capacity when working as (X position title) for (X organization). In this role, I was responsible for 10 sales representatives and (X further related responsibilities). I realize this particular experience is not related to this position, however the team management skills acquired in this role will highly benefit me in this position at your company. I thoroughly enjoyed taking on a leadership role as I love leading team members to success."