There are no perfect questions and there are no perfect answers. Just come as close as you can.
If a question is unclear to you, it is entirely appropriate to ask a clarifying question or paraphrase the question to make sure you understand. "Parrot back" the question in your own words to make sure you have the correct meaning. Do not assume you understand or make a "best guess" of what the interviewer is seeking. They are the only ones who truly know what they want, so a well-placed "Just so that I understand, what you are asking is…" response will serve you far better than treading down an unknown path.
The Parroting Technique will also serve you well as a temporary stall when you do not have a ready answer.