You might have a problem with the damsel. Depending on the type and size, they get pretty aggressive the larger they are. My opinion is that damsels are a fools fish. Cheap and look great when they are young, but get ugly and mean when old. Also, your clown could be somewhat aggressive if it has its own territory, probably not as aggressive as a maroon clown though. The good news is that the yellow tang should be able to hold its own against these two types of fish. The tangs come with a spine near the end of its tail that it uses to protect itself. The spine is pretty easy to see, little white thing pointing to the rear.
Good luck, I have a maroon clown and two yellow tangs and they can get nasty to new comers.