Thud when releasing clutch pedal

[Mark A]

Hi all, I have searched for this, but no joy - so apologies if this has been covered before.

I have a 2003 A4 1.9TDi with 80K on the clock. When I am in traffic & working the clutch pedal quite a bit, I notice a thud when I let the clutch pedal out (sounds as if it's coming from the back of the car). Is this a fairly common thing, and is it easy to rectify.

Cheers,
Mark