Thanks all! I actually got it off by accident with a 4x4 and 2x4 scrap.
My idea was to hold it up with the 4x4, with the added bonus of it applying the upward pressure on the clip itself, then to use a 2x4 scrap as a pounding block and smack it with a hammer.
My 4x4 scrap was too short, so I went and stuck a 2x4 scrap underneath it.
Lo and behold, the wobbling that combination caused both pushed and bent the clip and it simply popped off the crossbar.
This is by far the dumbest luck I’ve had yet working on a grill.