Can it work? Yes. Will it work? Can't say for sure. That clam could be what changes your flame from a model citizen to a standard angelfish and have it go nuts on anything and everything in the tank. That being said, is the flame angel or the clam more important to you?
Maybe okay for a while if you feed multiple times a day and it has plenty of live rock to graze on. Then one day they flip a switch and go rouge without warning. Risky.