Well mate - You play bass? Then please explain why it is not difficult. Are you able to play any AC/DC song in the same style Cliff does?
It is not difficult because he sit on the root note 99% of the time. The technique is all in keeping a solid tempo for the simplest bass line you can imagine. It sounds great but it is not hard. I could not do it as well as him, because I have not been playing every night for 30+ years. I would find it a challenge to play the same note continuously and in time due to repetetiveness .
Are you able to play any AC/DC song in the same style Cliff does?
I was always too busy writing my own basslines away from root notes to learn anyone else's.