What is this mark?

[Noesph]

I've got a little Renault Twingo gt (Silver or Mercury as Renault calls it). The rest of the car is in good condition but there is a brown mark on top of the bonnet. I've tried polishing it out, clay bar etc (Poorboys white diamond, and megs clay bar kit). It might have improved a little bit but its still there.

To be honest I don't really know what it is, or what caused it.