Check around interior by clutch pedal. Look up. If damp, leaky master.
Pull plug outta bottom of bellhousing. If brake fluid, slave cylinder.
If no leaks, and comes and goes, master cyl is leaking by seal, but staying in closed loop.
STC500100 Master fits 200/300 tdi i believe
FTC5202T is TRW Slave for same app.
If clutch fork....beyond my recent knowledge.
KGH - Defender Snob