Yeah the clip is probably shot on the fitting so it no longer holds. The ones one amazon that come with fittings are a few dollars more and you will have some spares that way. It is a PC4-M6, might be a good time to get one that comes with a kit an a capricorn tube to make the whole system a little better. This one is the same price and has 2 fittings along with the tube for 7 bucks although does not have the capricorn tube.
If it is the new style fitting it is available here: https://gigdigit.com/bowden-connector-for-new-type-extruder-feeder-mechanism/