If you're dead set on CLISP you'll have to use StumpWM 1.0.0, the latest and
last release to support multiple lisps. The git version (for which a new
release is imminent) only supports SBCL. This was to remove maintenance
overhead and to further solidify the common lisp community around SBCL.
The de facto way to install lisp dependencies is with quicklisp. So you'll
follow those instructions and substitute clisp where sbcl is used. Then it
should be a matter of './configure --lisp=clisp; make; make install' to get it
compiled and installed. We'll help you as best we can, but we can't fix any
bugs you encounter. A newer modern way of managing multiple lisps is roswell,
so you make look into that as well.
You're welcome to submit patches that can be applied to the current codebase,
but I won't accept anything that is clisp dependent or works around clisp