On your Mac, in the TV app, find your home video in the Library. When set to Grid view (with the 16:9 tiles), you can hover the mouse pointer over the tile, to see additional control buttons. Control-click (or right-click) the (⋯) More button for a contextual menu. Choose ‘Show in Finder’ to open the Finder window that has that file in it.
Then transfer the file to any other disk, local or in the cloud, of your choosing. After confirming that the transfer went well, you can then delete the source file on your Mac. Choose ‘Delete from Library’ through the previously mentioned contextual menu. It will then offer to optionally remove the source file as well as the Library database entry.