Yes, though it may not be the best idea. If the lion gets stung once,it will realize the anenome is a threat to be avoided--but that first encounter may be lethal if the anenome. I had a curly-que in with my lion, and he figured out very quickly to avoid it, while the puffer in the same tank never caught on and constantly had little white puckers from stings. With a larger anenome, if might be able to actually eat the fish in that first encounter, though--I'd be careful on that account.
Further--anenomes are specialized animals, and the high nitrates that often are found in with predators will not make it happy. Do lots of research before purchasing one.