Typically what you have it a piece of heater hose and a carriage bolt or hex bolt with a flat washer, when you tighten the bolt it compresses the hose.
I'd take a thin blade screw driver and try working around the outside of the hose to break it loose from the frame tube.
Maybe try to spray some WD40 in the hole to help loosed things up.
In one case I pushed the bolt all the way in so I could pry the hose out, then tip the frame up to get the bolt out.
Once apart I sprayed with WD40 and used a rag on a screw driver to clean the crud out of the frame tube.
Then replace with new hose and new bolts.