Posted by larry phelan 1 on 19/11/2020 17:02:48:
Give the dog a bone and let him sleep !
Stick a piece of plastic over it and forget you ever saw it.
This 
By the way, it's the layshaft bearing for the high/low gears on a two-speed mini-lathe.
If you do want to replace it you would probably need to remove the headstock from underneath (4 screws IIRC). Make a note of how things are arranged then remove the clip from the shaft and slide it rewards until free of the bearing, which can then be drifted out using a bar through the shaft hole and new one pressed in (no great force needed, put a wooden block on it and tap gently into place.
Make sure the gears and any spacers and shifter fork are all in the right place otherwise "assembly is the opposite of dis-assembly".
Neil