can you spray over clear parts?

The only thing I ever put on clear parts is Future (sometimes.) Anything else, I would suggest you test first, on scrap clear plastic.  The clear coats might contain something that would cloud the part.

If the parts have flaws or flash that needs cleaning up with very fine sandpaper I use clearcoat to restore the transparency to remove the frost that sandpaper leaves.

BTW, if I am heavily weathering a model, I don't want the plexiglas to be to shiney.  Plexiglas, especially before the sixties, the plastic faded from UV as soon as it was exposed to sunlight, and would end up pretty foggy looking.  Had to replace windshield on an old 1:1 plane I bought.

Clear flats,  Dullcoat lacquer, etc. will cloud the transparency.   Not recommended if you want to see through.  Same for satin coats

Clear gloss might not cloud the transparent part as much but will still affect the appearance.   Gloss coat lacquer needs to be judiciously thinned - the thinner may craze the plastic finish

This becomes a really issue for passenger airliner models.

You really want to mask the clear.

And any hot lacquers- death.

got it.  will tape and play it safe as i want to keep it transparent.  tks.

I have never had glosscoat, even the lacquer version, dull a kit transparency.  I don't know why- I wonder myself why. Maybe the kit transparencies are acrylic, not styrene.  They do seem harder than styrene.

I have airbrushed a light coat of dullcoat on the tops of canopies on aircraft I am going to heavily weather.  The acrylic canopies on older aircraft, WW2 and earlier, were not UV stabilized and faded/frosted after a couple of years in sunlight.

Hi Don;

      That's why some folks don't understand the costs of old aircraft. Tap Plastics in California had to make new Plexi panels for the  B -25 in many areas. Cost more than a new Kia Soul Today!

       As far as models I have never had a problem on that subject except one model that bugged me for years. I had gotten a Vac-Molded kit of a Pembroke. When I cleared it the windshield area  fogged. I had to remove it and make a new one out of Vacu-Formed styrene sheet!

 All I can say is I sure am glad I still have that Mattel "Vac-U-Form" machine . This is the second one. Someone permanently ( I don't know who ) borrowed the first one I had. This one has the original box, plastic panels and molds. It made( for the time ) some real cute little cars and stuff.

So I taped to be safe. Then, experimenting, I left the rear roof window untaped. No issue. Still crystal clear.