Yes raw meat can be cooked in a slow cooker and as the slow cooker is cooking the other foods the meat will also cook.
I never cook meat first before putting it into the slow cooker and it's always cooked the meat all the way through.
I will sometimes make beans as well as ground beef added to the beans and just place the ground beef into the slow cooker along with the beans.
The ground beef when raw cooks just fine along with the beans.
You can cook the raw meat first before slow cooking it but the slow cooker will cook the raw meat which is the point of a slow cooker.
Just add the raw meat and any other foods and after 8 hours or so the food will be cooked and ready to eat.