I would say right now the clown HAS to live alone in order for your anemone to survive. First thing first, you NEED to put some covers (pantyhose) over the power head (water movers) intakes. This is a must when having anemones, as they have a very soft skin that can get caught inside them. Maroon clowns are very agressive hosters and will beat the tar out of an anemone, especially if they are much larger than the anemone (my guess is this is your case).
I don't think with a torn foot the anemone will last long. Just ensure that nothing is bugging it, reduce your flow in your tank and try to see if over time it will recover on its own. I hope you have adequate lights to help the health of the anemone (T5 or MH), otherwise the anemone is going to die no matter what - torn foot or not.
My suggestion would be to nurse the anemone back to health, if you can. Let it become established in the tank, grown, then reintroduce the clown once the anemone is A LOT larger than the clown. The anemone need to have a firm grip on the sand/rocks and become healthy before you think about reintroducing the clown.
Keep an eye on the anemone, if it dies it will start to fall apart and foul up your tank in a hurry, take it out if this is the case. And if this happens and you purchase another anemone PLEASE get one much larger than the clown, and cover your intakes or you will be in this same situation.
Good luck.
