I have two clowns my self and a coral beauty angel and from my experience the angel has been a little abrasive with my clowns. She likes to challenge their ownership of their territory some times and they might get a little nippy. As a matter of fact, about two weeks ago, my female clown developed what seemed to be popeye. I just let her be and slowly she healed. My theory is that she got hurt while nipping with the angel and it got infected. I'm not saying you should do nothing, but in my case, since I don't have anything set up, I determined that the stress of moving her to isolation for treatment would make things worst. Thankfully she recovered. I was lucky she didn't stop eating so I put some selco in the food to help out. That's why I asked about your other fish.
If you just introduced the clowns and the angel was established in there already she would've definitely moved on them. What kind of angel btw?