Payson,
Does your closer look like the one pictured?
If so, you should be able to reach down in that slot with a pick/scribe like one in center photo. 1st rotate the tube around so you can see the butt ends of the wire clip below the slot. Reach down with the scribe at a slight angle which the slot should allow, and push the point of the scribe under one end of the clip. The trick is to get it up out of the groove. while holding the end up with the scribe, reach down with the other tool (just a heated and bent pocket screw driver) and pull that end of the clip out of the groove. You should then be able to work your way around with the screwdriver or similar tool and pull it out of the groove the rest of the way. Then you can work it to the top to clear the collar so you can slide it off the tube the rest of the way.
I'm sure there are special tool for this but with the 2 simple tools pictures, it should only take a couple of minutes.
Hope this helps,
CWC(4)