I’m not sure exactly what you mean. If you are talking about a menu directly in the admin panel, you’d be better off just using the WordPress API add_menu_page to create a menu item and use its callback. If you’re talking about a submenu item, it would still be easier to use the WordPress API add_submenu_pageand its callback. If it’s a submenu already created by Redux, the only solution I can think of, untested, is to use custom JavaScript to capture the click event on that specific menu item, halt it with preventDefault and use AJAX to run whatever PHP you needed.
It’s advanced stuff that’d require some JavaScript and PHP know-how.
Good luck.