very difficult to see, but to answer your last question, yes...it is very typical for them to want to hide and acclimate themselves to our conditions and lighting.
This could be happening for multiple reasons including feeding it...
Everyone has their own techniques but I personally try to refrain from direct feedings when I introduce a new nem to my tank...
I also prefer to feed small offerings of mysis until they are fully settled into their "happy place". Then I offer 1/4" size chunks of raw shrimp as well a few times a month.
This may also just be a case of "I wanna hide but can't seem to find a rock to hide in" syndrome as well....
You can either try to remove it from its glass corner and set it on your rocks (I would do so with as little water flow as possible to give it time to anchor itself) or I would suggest covering your tank with 2-3 layers of window screening (use eggcrate to cover your tank temporarily if you don't have a screen cover already) and remove a layer every 5-7 days to acclimate the nem to your lighting...
I'm sure the clowns are irritating it as well but not much you can do about that unless you isolate the clowns temporarily...
GL