It's the entire song recorded live so at about 6:58 you'll see the camera move from Entwhistle and the bass drops out as the other instruments begin the final section with the bass resuming at 8:08.
Seeing this performance of John Entwhistle in isolation really does support the claim The Who were 3 lead instuments playing at once with Daltry's vocals on top.
If you ever wondered why John Entwhistle was called "The Ox" we might know after seeing this video (there were other reasons), the shear stamina and strength for a bass player to keep this cascade of notes going and in context of the song is simply jaw dropping. The whole thing is like an extended bass solo. No surprise the man was to change how other players conceived a bass role although few could ever achieve this level of strength and power.
A couple of points to look out for. It's possible he plays a wrong note in the run at 1:27 and immediately after smiles in recognition. But that is just the one note you'll understand.
Then right at the end of the song and the final crescendo of feedback he's using and the absolute nonchalance of the shut down of the instrument, the stage is immediately invaded by fan who embraces Daltry and the ambling figure of him mooching across shot is priceless. It was just another day in the office.
The entire piece is one of the most extraordinary recordings you'll see of any musicians skill and constituent part of a live rock band.
The film looks like it was The Who in September 1978 (search that) and if so was the last gig before Keith Moon's death on September 7th. John Entwhistle died in 2002.
