Worrying brake clunking noise.

[Lungbutter]

My brakes (pretty sure it's the front ones) have started making a clunk when applied. This became more apparent when carrying a lot of weight in the car recently.

I dismantled the caliper, checked it over and re-assembled it but the problem is still there.

Now I know my discs are in need of replacement but could this cause the clunking noise?

Ooops, I forgot to mention it's a 2000 A6 quattro.