The Inspector lets you examine and destructively modify the contents of Common Lisp objects. It is an invaluable tool during development, since it lets you inspect the state of any part of your data at any stage during execution. Thus, it is easy to see the value of a slot and, if necessary, alter its value, so that you can test out the effects of such an alteration before you make the changes necessary in the source code itself.
LispWorks IDE User Guide (Windows version) - 25 Nov 2011