weird i thought Clarkii were the easiest to be hosted by an anenome. Percs are not easily tempted and it took me about 4 months to get mine to sit inside the RBTA. He never leaves it now
and the trick is i put actual pictures of a similar fish inside an RBTA and after few days he is in it! A fellow reefer suggested this. I did it wiht a lot of skeptisim but it worked. My suggestion try to find an image of a clarkii inside an anenome and tape it to the tank for few days. it may work