Elegance corals are very finicky. I don't believe there is much you can do to keep the clown from hosting it short of removing one or the other from the tank. I can say that the clown can hurt the elegance. Their flesh is tender and their skeleton sharp, so a rub the wrong way can cause the flesh to abrade which often means the end of the coral. I had an issue with hermits walking over mine, their feet would poke holes.
It's a pretty coral, would you rather have it or hosting clowns?
You might be able to put a tank divider in and get a small bubble tip anemone. Keep the clown and anemone together until the clown starts hosting it. If it's like my clowns though, it will host multiple things in the tank so I don't know that it would get the result you're looking for.