does anyone know what it means to clean a chapter

Probably to erase the original text so that they can put the translation on top

It means prepare it for type-setting.
You need to erase all the text there is.
It also means removing every sfx youre capable of.
That's basicly it for this title.

I also removed some dust and repared quality a little as lezhin (original site where artist posts it in korean) kills it a bit :<

If you want to know how cleaning of the manga (black and white) scans is made it's a lot longer process :)

thanx(￣∇￣")