It looks like app-admin/cronolog was last updated upstream in circa 2013. I believe modern syslog tools more or less reproduce its feature-set. This ebuild is using EAPI 6 which has been deprecated.
Is the package broken, or just old? If it is broken, please add the logs as usual. If it is just old but still works and upstream is still available there is no reason to tree clean it. There are sometimes users who have a good reason to use old software, but we do not know about it. We do not want to disrupt their system without need.