Recs.
Updated
A modern lisp, with efficient, persistent data structures, targeting javascript as a runtime.
SpecsUpdate
Pros
Pro Live interactive programming with figwheel
Figwheel builds your ClojureScript code and hot loads it into the browser as you are coding! Every time you save your ClojureScript source file, the changes are sent to the browser so that you can see the effects of modifying your code in real time.
Pro Excellent tools for web development
ClojureScript has superb wrappers around React.js (see Reagent) that make building single-page apps a breeze. With figwheel, it's a web dev experience unlike any other -- hotloaded code, repl interaction, and instantly reflected changes make good development fun and fast. You can add things like Garden to make CSS-writing part of the same holistic experience and suddenly all development is a pleasant, smooth process.
Pro Targets js instead of the jvm
The jvm is too heavy for many use cases, and obviously isn't an option in the browser. Clojurescript can target both node and browsers, and so is another great option for full stack engineering. Servers or scripts and cli's in node, thick client apps in the browser, and all the rest.
Pro Starting with clojure means you have less to unlearn that if you come to it later in life
Cons
Con Depends on JavaScript
ClojureScript is a hosted language that depends on JavaScript for basic tasks. Beginners learning ClojureScript have to learn two languages instead of one. You might as well start with JavaScript and learn ClojureScript second.