Strange clunking/clicking sound from the rear end

Can anyone point me in the right direction, please? Here's a video link: https://www.dropbox.com/scl/fi/l53x6qbbqlqnohkqyacop/Untitled-Project-2dd.mov?rlkey=ocq8uiavjazx8cjldy3zon5d2&st=2y5pnowv&dl=0

For context, I haven't drove the car in about 4 years. I have stripped and rebuilt the car front to back, so I've obviously made an error somewhere, but It sounds like it's coming from the rear end