If you're interested in using Titan from Clojure, then you'll probably want to take a look at Titanium[0] and Ogre[1]. We've been working hard to make these libraries as useful as possible. If you have any questions about how to get started, then please get in touch! My contact information is in my profile. I've been immersed pretty deep in this stack lately and it's been pretty rewarding so far.
[0] http://titanium.clojurewerkz.org/
[1] http://ogre.clojurewerkz.org/