If it is some kind of grease or oil smear, try some automotive wax and grease remover (prepsol) and see if that removes it. But looking at the picture, it looks like an area that has been sanded and attempted polishing. I would try the prepsol option first, then use some polish and see if it will hand polish up.

 

It looks to me like a crude attempt to remove a flaw in the paintwork, using very fine sandpaper.
From my tools I would use Tamiya polishing compounds and their wax treatment.
I would be inclined to work across the whole roof, reducing the potential for uneven results.
I have a 1/24th scale project on the go, and when the paint cures this is the technique I will use on it.

 

I have a few AutoWorld models, all of them were poorly crafted & assembled and have paint issues.

That might be a simple polish fix with some medium abrasive compound and then buff to finish, just like you'd do on a real car.

But in case that doesn't work: one of the members here, Eric, used Novus plastic polish to repair paint rash on a black AutoArt Diablo 6.0.

I know that is a different issue to the one you have, but the method might work all the same.

Here's the link: https://www.diecastx...ing-and-polish/

 

I'd start out by polishing it, if it has a clear coat on it, nothing will happen. If the model is not cleared (which is what you want) colour will come off on the cloth and you will know that it has worked.