As someone who runs a department and conducted my fair share of interviews over the last several years, I'd have to say that interview question is much more of a "goal" oriented question, which really could be anything you hope to accomplish as a lawyer. Of course, our main goal is to have a job, but add something like you want to be published in a law journal, or the managing partner of a small firm, etc.
Try to make the goal match where you are being interviewed so you don't tell the medical malpractice lawyer that you see yourself fighting crime with the District Attorney's office in five years. Sounds like common sense, but you'd be surprised as to the many interview mistakes people make without even realizing it.
So just evaluate some of your goals as an attorney, and add them to your five-year plan. You should also do some practice interviews with a friend. It might sound a bit overboard, but jobs are very competitive. So when you actually get an interview, you want to make sure you get the job. If it's a temporary job, tie in the work as a stepping stone for your goal, etc. Hope that helps.