CAS (Central Authentication Service) is a single-sign-on service (say that several times quickly) and through accessing a CAS /logout URL, as an application, you’re able to log the given user out. What wasn’t clear (by Googling) was whether there’s a possibility to redirect the user back to the original application (or a given URL). I now know, thanks to the CAS Protocol Documentation (section 2.3), that any posts that mention adding ?service=http://my.url/ to the /logout URL are incorrect, as this isn’t a valid parameter (at least not at time of writing).
However, you can add a ?url=http://my.url/ to the logout URL and get this (likely, depends on your CAS settings) displayed as a link on the logout page. So, a full URL like this is good to go: