It's not likely that the feather duster is going to tolerate the clown aggravating it. I would keep a close eye on things, and remove either the duster or the clown at the first sign of a problem. Clowns can get very rough with whatever they are wanting to host in, they have been known to tear up and/or kill corals and such while attempting to host.

I suspect you will be forced to either remove the clown or duster, or watch the duster die.