A common approach to end-users: . Using the Views module , you create a view page (with its own path) that shows only the last (or n last) node (s). Then you indicate your menu item on this page.
An alternative approach Developer . If you want to avoid the overhead of the views module, you can also implement it hook_menu()in the user module. There you would register a callback function for the new path (for example, "/ show / latest / news"). The callback function will then determine the latest node news and either make it itself or redirect its path using drupal_goto(). Your menu item will point to a new path.