Just bought a second hand frame and on inspection it’s got a Tiny ‘crack’ at top of head tube. Pretty sure it’s just a crack in clear coat but I can confirm that by removing about a cm sq of paint.

What’s the best way to do this, I’m assuming very fine grit sand paper to take off the clear coat/ paint? Then what? Do I need to repaint to protect?

Ta

What if it is or inst a crack? Will you be able to return the frame after you have ruined the paint?

If eBay, I’d just ask for a return and refund.
If you take the paint off you won’t be able to return it.
If it’s a private sale I’d ask the seller’s opinion, though they’re likely to just deny it, caveat emptor and so on.

fine grit sand paper to take off the clear coat/ paint? Then what? Do I need to repaint to protect?

I had an old road frame that I stopped riding because of a crack – got curious at how bad the crack was, so took a random piece of sandpaper too it. It sanded down to the reveal the damage very easily.
There’s nothing to protect if there’s no crack. Just plonk a sticker over it 🙂

I did this recently on a carbon frame that I thought had a crack – did it most neatly by scraping the laquer/paint with a scalpel blade on a tiny area only a few mm’s wide, whereas sandpaper will leave a larger area of damage. An Led strip and good magnifying glass also useful to inspect what’s going on. Luckily for me it was just a crack in the paint layer in an area of flex, worth doing for peace of mind and just left it as a tiny battle scar.