Clojure has good web libraries, and Clojurescript compile-to-js means you can write both the back- and front-end in Clojure.
For what it's worth, Amazon's back end used to be C and Common Lisp, and they've recently posted openings for Clojure devs.
I mean, even Scheme has web server libraries (and if you want something simple, it's not a bad choice). But if you want a LISP with extensive web frameworks and protocols, Clojure is really it. Arc just doesn't have the popularity—when you hit walls, it's going to be hard to find help.