The coral looks a little more like a trachy than a wellso. Regardless, the clown will cause it stress and if the coral is new to the tank it is more likely to die.
I would recommend you move the coral and wait for the clownfish to take a new host. (If you have a frag tank or other tank. I had a trachy that died due to the stress of a clown. I tried covering the trachy with a clear glass bowl, but I wasn't successful.