Converting light socket to outlet, what do I do with ground?
The proper thing to do here would be to free the wire from that clip and then wire nut that bare copper wire with two additional bare copper wire pigtails. Green wire nut would be ideal. One of the pigtails will go to the green screw on the outlet assembly. The other bare wire pigtail needs to be connected to the box. It is unknown if the clip can be used again so barring any judgement I would look to see if the electrical box has a pre-threaded hole in the back. The threaded hole is intended to accommodate a green box grounding screw. Get one and use it to attach the second bare pigtail to the back of the box. The picture below shows what appears to be the pre-threaded grounding hole in your box.