current-process-kill signals an error if it is called when interrupts are blocked, unless it is inside the scope of with-other-threads-disabled, in which case the process is marked as "dying", and actually dies on exit from with-other-threads-disabled.
If you have a process that is broken and repeatedly goes into the debugger and you are not interested in debugging it, then calling
current-process-kill is the best way of getting rid of it. This is especially useful on non-Cocoa platforms (GTK+ and Windows) when you get an interface that is badly broken.
LispWorks User Guide and Reference Manual - 13 Feb 2015