Clojure
Clojure could be a gentler-ish introduction to Lisp. They're strictly related, of course, but Clojure is bit less intimidating because it looks more like "normal" programming language, for those of us who come from old school imperative languages. This does not mean that it's an easy-peasy language, but simply that the learning curve is less steep if compared to Common Lisp.
That said, going down the Clojure road has some pitfalls. Its close relation with Java can be an issue for many - it's been for me, I swear - and its REPL debugger is (my opinion) much more cryptic than Lisp's.
More subtly, Clojure is often perceived as "the Lisp who wants to befriend Java", and Java is a quite demanding friend: what's good for it should be good for you too. Like, the most mentioned reference IDE for Clojure is IntelliJ (no thanks) or, at the opposite side of the usability spectrum, the good old Emacs with plugins (no thanks either).