Years since I had to fit a kick down cable on an automatic, but how do you say that plastic clip is broken?
To me the cable is probably fitting through a bolt with a hole in it and washers to pinch it in to place to allow more adjustment than the threaded outer cable in photo and the plastic bit just has a groove in it to guide the inner cable around the spool better.
Obviously you will adjust it so the kick down only actuates towards full throttle, but in a position that suites your driving preference.
Unless of course you have a genuine new kick down cable that just as an end that engages with the throttle cam.