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This looks to be a roll pin. It’s held in place because the outside diameter of the pin is slightly larger than the hole it fits into and the pin is squashed up. (The pin has a slit running all the way down it, and usually has one end which is tapered to allow it to be started in the hole).

You use roll pin punches to remove them and they usually come as a set. You use the one which is smaller than the hole so that you can hammer the pin out and withdraw the punch. if you’re cheap like me you can file the end off an appropriately narrow and long nail and use that. Just don’t use a tapered end nail as the can make the pin harder to remove