Do you mean cloning a feature? If so, you can read about that here. That article discusses cloning entire features which includes supporting pages for features.
If you mean, "How do I clone a CMS Page?", then the answer is there isn't a way to do that. If you want a page to be setup the same as an existing page, but with it's own data, you need to create the page and add the features to it that you want on it. If you want a page to use features that are on another page, with the same data, you can take a look at the Global Content setting.