There is a pin that runs through the spider gears to hold them in place. That pin has to be removed to move the axle in far enough to remove and install the clip.

There is one small bolt at one end of the pin to remove and the pin will come out. Once the pin is out the axle can be push further into the differential to remove and then install the pin.

If you are careful the gears will stay in place.

Really not a hard job to do once you get the pin out, and once the bolt is out it may fall out or take a light pressure to pull it out.