Anything that Java is used for

All sorts, but I believe it was born out of frustration at unnecessary complexity arising from standard enterprise development.

Hickey’s choice of hosting it on the JVM was ingenious, gives access to one of the largest most battle tested ecosystems in modern day enterprise engineering.

It’s much more versatile these days with the likes of ClojureScript, it’s being used in anything from real-time multimedia projects to SPA JavaScript work.

Basically anything other than operating systems. I've been working on an optimizing compiler for spreadsheets, and an event sourcing system with a WebSocket gateway in my current work.