The Tracer tool is a debugging aid which gives you an interface to the LispWorks trace
facilities. These allow you to follow the execution of particular functions and help you identify where errors occur during execution.
To create a Tracer, choose Tools > Tracer or click in the Podium. Alternatively, a tracer can be created or displayed from within many other tools by choosing the command Trace > Show in Tracer in any menu whose commands operate on a traceable symbol.
LispWorks IDE User Guide (Windows version) - 13 Sep 2017