The interviewer might be asking you this question because that “particular area” might be the “key performance area” for that role.If you possess experience in the domain/ area the interviewer is talking about, tell him that I possess a good experience in this area and then go on to discuss some important nitty gritties. You may also want to quote some example from past which demonstrates your performance in that field.For e.g. If the interviewer asks you about your experience in dealing with press, you can refer them to some of the items that you got released to the press and some other online material that supports your answer. Once an interviewer asked me about my experience in writing the press releases and getting them released. The best thing I could think of was to refer them to my online press releases. My work actually spoke for me and they were quite impressed with it.Remember, while in a telephonic interview, the chances of an interviewer sitting in front of a laptop connected to Internet are higher, so you can use this interview in your favour by providing them an example of your work even when they can’t see your portfolio.   _{Your Comment}