Ive think ive got the same thing but in 3rd & 4th

Ive been told that its common on Exedy clutches. As dunx correctly says its called "clutch thrash"

The springs in the centre plate arnt under tension when off the throttle, with the vibration of the engine these springs tend to vibrate and spin around which creates the noise.

It normally shuts up after a couple of thousand miles when some clutch dust gets around them

Hope this helps