It is a Rose Bubble Tip Anemone (RBTA)
If yours is having trouble eating, try to coax him. A silverside might be too big for him right now if he's sick.
You might try thawing some mysis and blowing some of the mysis bits and joice over him with the pumps low or off. If he responds by getting sticky enough to hold some of the mysis, then try to put a small piece of silverside on him.
Are you soaking the silverside in anything? There are a number of products out there aimed at coaxing "finicky" fish to eat. I really do think a HUFA, garlic, or spirulina type supplement to soak the silversides in wouldn't hurt.
The frozen Formula One or VHP formula is a good way to get something in them that is easy for them to digest as well. If you thaw it at room temperature, it keeps a texture firm enough to hold together, but soft enough to eat easily. I'd cut a cube in half or maybe even a quarter to start if you go that route.
If the anemone isn't sticky enough to hold it, though, the clowns and your other fish will just grab and eat it.
I'm no expert as I only have experience with my own anemone. But these are things that have worked for me so I offer in hopes that some of it may work for you.
Fortunately, good light will help him even if he doesn't eat right away.
Good luck!
Cathy