OMG. We used CLU in a software engineering. The compiler (really a CLU-to-C translator I think?) was sooooo painfully slow. Can't imagine using it for anything moderately complicated.
I know what CLU the language is and its significance, but every time I read about CLU I still think: "Forget it, Mr. High and Mighty Master Control. You aren't making me talk."
Just chipping in that an early CLU compiler for the PDP-10 has been recovered from backup tapes, and can be run on an emulator.