To use it, highlight a word as the X selection, and click on the Webster button; if all goes well, you will soon see a popup containing the definition of the word.
By default, this client produces a button on your tkgoodstuff panel. But you can set preferences so that it will not, in which case you can use the (tcl) command "WebsterDefine" as a Menu client item.
This client has its own Webster client code, so you do not need the "webster" unix program installed on your machine. However, because of kludges needed to work around (temporary) inadequacies in Tcl, the "webster" program is more bulletproof, and so there is a preference that, if set, instructs this client to use the "webster" program rather than its internal code.
Client WebsterAll parameters are adjustable in the preferences manager.