If the clowns are already hosting a specific area of the tank, move the anenome over to them. My clowns were hosting the right-side, back corner of my tank, and my anenome was in the middle of the tank. They stayed separated for months. After a while, I moved the rock that the anenome was on over to the corner where the clowns were, and within 1 hour, they were all joined at the hip. Only thing was that the anenome didn't like the corner, so it moved. The good thing is that the clowns moved with it back to the center of the tank.
Best of luck!!!