Especially if you are familiar with the JVM, then I think Clojure is an excellent first Lisp.
If you'd like to stray into other flavours, then Racket is an excellent choice (and Dr. Racket is an excellent dev environment). Alternatively, Gambit Scheme might be attractive insofar as
clojure-scheme compiles down to Gambit (and thereby to C). I don't think learning these will help you learn Clojure; but, they do do certain things differently that will nevertheless be useful to you in helping you think through various kinds of problems.