Compresser rattles

[D.Slatford]

Put the Xantia (1.9TD 1997) up high this evening to see if it was me leaving little spots of oil on the road. In doing so discovered something else worrying. An occasional loud rattling started as the car went up, from the front. Looking underneath it, at the aircon compresser, the front of its flywheel was sort of rotating, loose enough to be able to stop it with my finger. Figured it's the clutch, turned aircon on to see if it engages, but still able to stop it with my finger, even rotate it backwards. Pressing it inwards results in a loud scraping noise, rather like the quietish continuous scraping noise I hear with the car on idle.
This doesn't sound normal.. is this the aircon clutch, should I be able to move it with my fingers regardless of the auxillary belt drive, does it sound like it needs replacing before something bad happens? How expensive is a replacement likely to be? It's covered in green gunk underneath too, probably explaining where my refridgerant went...

[bernie]

It would appear that the bearing has broken up big time[}:)], they are available seperately