I'm not sure clojure should be the language of choice to compile anything. At that point you might as well implement elisp as a hosted language as well. What papaw was saying up above was creating an elisp compiler for common lisp will make it portable to native code via sbcl and hosted code via sbcl.

I suppose one could argue writing it in clojure would make it portable to both the jvm and any javascript engine but what clojure project of significant complexity doesn't break out into the host language from time to time

What compilers have been written so far in idiomatic clojure?

EDIT: since I'm thinking about it could anyone imagine debugging a compiler in clojure? Talk about stacks on stacks on stacks...