Can you put clear coat over krylon fusion paint?

Yes You Can,

This info came directly from Krylon about clear coating their Fusion Paint.

Thank you for your inquiry with Krylon. While the Fusion is a hard, protective, durable finish on its own, the film is not impervious. Keep in mind, Fusion is still a paint coating and can be nicked, scratched, or damaged. Consistent friction or direct pressure with a sharp object will damage the film. Please allow the last coat of Fusion to dry for 7-10 days to reach the film's maximum hardness and cure time.

If you would like to add a sacrificial clear coating over the Fusion, I would suggest using the Krylon Low Odor Clear Finish or the Minwax Polycrylic. Both of these clear coatings may be applied to a fully cured Fusion paint film. Please allow the last coat of Fusion to dry for at least 7-10 days before top coating.

NOTE: Technically you are applying a clear finish that will take the brunt of daily wear and tear before the underlying paint film. The clear finish will not be any easier to touch up and recoat then just applying an additional coat of the Fusion paint. This is the reason we do not offer a clear finish in the Fusion Line. The clear finish will not be any more durable than the Fusion paint film; but may not show the wear as quickly because of the transparent nature of clear films.