Fran the tapered trace function works on two clines of different widths only. No DRC must exist on the net for it to work.
Try this as a test. Draw a trace with a width of 50 mil for about an inch in length then reduce the trace width down to say 25 mils and continue on routing for about an inch.
Go to the gloss menu "Route > Gloss > Fillet Parameters.
Check the option at the bottom of the window "Tapered Traces" I set a desired angle of 60 and a offset of 200, click ok to dismiss the dialog.
Go back to the route gloss menu and select add a tapered trace. in the find menu make sure cline is checked. Draw a box with your cursor around the point where the 50 mil trace intersects with the 25 mil trace and a little fillet will be put in to taper the trace.
Hope that helps,
Quick edit here, Fran in your picture I am not sure if that is a pin that the trace is connected to or not. If it is a pin then you dont need to use the tapered trace option. Just use a fillet instead. Come off the pin with a trace of a suitable size and then gloss it with a fillet.