Clojure is a Lisp-1, yes. Think of it as a nicer Common Lisp without all the historical baggage. It also has several modern concurrency features like STM and Agents (they decided not to implement Erlang's Actors model). The advantage of running on the JVM is simple- there are already SO many libraries written for it (mostly in Java).
Clojure in Clojure is an ongoing effort to rewrite the Clojure compiler in Clojure, to make it more portable and maintainable. Apart from core.clj, most of Clojure is written in Java presently. After this move, it'll be possible to port it to a LOT of VMs, including Parrot.
