With the option
Editor keys like Emacs, Alt is Meta key
acts as Meta when the input focus is in any
within any IDE tool. This includes the Text area of the Editor tool, the Listener area of the Listener tool, the Output areas of several tools, the echo area seen near the bottom of all tool windows, and graphs such as the Superclasses and Subclasses areas of the Class Browser.
LispWorks IDE User Guide (Windows version) - 25 Nov 2011