Campden should be used, and it will fall clear. I don't know if anyone on this board has used finings for cider- that might help if it doesn't want to clear. I think patience will do it, though- it should eventually clear on its own.
__________________ Broken Leg Brewery
Giving beer a leg to stand on since 2006
You only really need to use campden if you use unpasterized apple juice. You add it at the start to suppress wild yeasts that may be present. Once your yeast kicks off you don't need worry about it.
Clearing ciders can be tricky but long secondaries usually does the trick for me.