I have looked everywhere for information on this... what does pclean do?
The program 'pclean' is currently not installed. You can install it by typing:
apt install pbuilder-scripts
pclean
is just a wrapper for pbuilder --clean
, and from the manpage of pbuilder:
--clean
Cleans up the directory specified by the configuration
BUILDPLACE and APTCACHE specified in /etc/pbuilderrc