Here the clubs are juggled in a regular cascade with double spins. While one hand makes a throw, the other hand swings the club which it is holding round in an arm's length circle, perpendicular to the body plane, and arriving back in front of you in time to catch the incoming club.
Try this with 3 balls first, just to get used to the rhythm. The direction of the circles doesn't really matter and it works both ways round. It is often the case with tricks such as this one, where you have a choice between two techniques, that you will find one way a lot easier than the other - so make sure to try both directions of arm circle before you start investing hours of practice time. In my experience most people will probably find the direction shown above to be the easiest one, i.e. the club goes up at the front and then down at the back.
When you first try arm circles with clubs do the circles quicker than you need to, and make sure that your arm has stopped completely before you throw. If you try to make it all a continuous movement, rather than start/stop, it is very easy to give the clubs too much spin because of your arm's swinging motion. Of course, once you are confident with the trick it will look much nicer done smoothly.
This trick was popularised by an American called Cindy Marvell, who won the IJA championships in 1989 with a club routine that featured it.