This is quite simple. I don't see many right answers so this is what I suggest. You can believe in two of the following. One, you believe that failure is not achieving your goal no matter what. Or two, you can believe failure is only when nothing is learned from the failure. I believe in the latter, but you don't have to agree with me.
Nobody wants a failure. So you can feel that answering like this will be risky. However, this is a solid answer that most people agree with. If the person doesn't like this answer, then you might not want to work for this person. Everyone fails and if you work for someone who doesn't tolerate failure, then you will be in a difficult situation. Even vice presidents of large corporations will believe that learning from mistakes is a valuable lesson. This answer also states that you will do you best not to fail, but just in case, you want to gain something from your experience.