Most will say to stay away from clear and for good reasons as It will yellow and flake off with age (been there and done that with clear lacquer & enamels).
I sprayed a new gas tank in 1987 with DuPont Imron polyurethane clear and when dried took the gloss down with a few passed of Scotch Bright for a natural look. To date there is absolutely no yellow or flaking.
As for brake lines, they are protected by a variety of methods out of the box. But to keep oxidation in check I often applied a thin coat of Birchwood Casey Dri-Touch with a small paint brush twice a year to the lines and armor and they still are clean after 25 years.
There are many opinions and methods, but this has worked for me in the long haul of 25 years.