Actually your condy is hosting your clown, but no it is not unusual especially if your clown is a clarki or tomato clown. A condy's sting is too powerful for some clowns, but clarkis and tomatoes don't seem to mind as much.
It is pretty common for clowns that don't have an available natural host to find an "unnatural" host. Various LPS corals, Green star polyps, zoanthids, hairy mushrooms, clay flower pots, even clams have been used as hosts by clowns in aquariums.