This question is very similar to the one about making a mistake, and you should approach your answer in much the same way. Make sure you pick a real, actual failure you can speak honestly about. Start by making it clear to the interviewer how you define failure. For instance: “As a manager, I consider it a failure whenever I’m caught by surprise. I strive to know what’s going on with my team and their work.” Then situate your story in relation to that definition and explain what happened. Finally, don’t forget to share what you learned. It’s OK to fail—everyone does sometimes—but it’s important to show that you took something from the experience.