Flames tend to not touch Clams, Corals etc if you keep them well fed I've found but it also depends on the Angel. They all have different personalities and tempermants. Some might pick a little. Just be cautious.
IME they are not reef safe. Mine nearly wrecked my reef several yrs ago. I had to take the tank apart to get him. He was well fed but still went after corals. You can feed all you want but eventually instinct will take over. He was a model citizen for 4 yrs but than went coral crazy. I`m sure you`ll get responses both way but as I stated IME NO they are not. I have taken the NO ANGELS pledge. BTW as far as the clam I`ve never had any problem.
I have had 3 flame angels. The one that I have now I have only had for one week. He spends every waking minute picking at my live rock and any other rock like substance in the tank with a never ending appetite. I would not recommend a flame angel in a reef tank.