Layered mylar, perhaps?

A pic of the area would be helpful....

However, without that, if the paint is still intact I'd get that playfield 100% level in all directions and would fill that divot/dent with clearcoat applied with a dropper, similar to how a cupped insert can be fixed.

If there is paint/artwork damage, a light application of bondo followed by some light small area sanding and touchup paint.

Check out vid's playfield restoration thread, 100's of great examples and ideas in it.

any pics ?

I have used epoxy or triple-thick polyurethane to fix similar playfield wear: epoxy for bigger work, the polyurethane for more precise.

I use layered round vinyl decal disk to fill in cupped inserts on old EMs. They are different diameters and they go smaller to larger completely leveling out the insert. Would be a quick easy fix.

I had a bad trail mark in my lotr from a screw dragging on balrog. used plastic wood to fill it up, then just sanded smooth. worked/held up great and that's 4 yrs ago.

Is there a playfield protector for this game?

I would try as best I could to color match the paint in that area, and put it in thick or a few coats until it was more level then spray a little topcoat like polycrylic over it.