A "clean lap" in Time Trial is one that is not invalidated by any of the following:
> Putting 4 wheels off the track.
> Making heavy contact with the walls.
> Using Flashbacks.
> Invalidating the final corner(s) of the previous laps.
The shortest track in F1 2018
is Suzuka Short but any track will do for this Achievement.
You can also multitask this with the following:
The Patent pending achievement in F1 2018 worth 57 pointsSet a valid Time Trial lap with a set up taken from a rival ghost