We no longer provide ClamAV packages (and haven’t for a few years). You should switch to the EPEL repositories for ClamAV. You may have to turn it off in Virtualmin and back on again to get it to create/start the right service, I don’t recall the state of migrating between the vm packages and EPEL packages (they changed package layout several times, and so did we…ClamAV packaging has always been a mess, partly due to upstream and partly due to packagers not being able to settle on a sane way to package the thing).
Edit: You’ll probably also want to switch to the newer Virtualmin 6 repos, too (they’re only new in the sense that they’re newer than the old ones, they’ve been around for two or three years). The Virtualmin 5 (and below) repos will be going away when Virtualmin 7 is released (which is long delayed but now imminent since I’ve mostly finished the new website/billing system and I can focus on Virtualmin itself again).