Path of a projectile (10)
I believe the answer is:
trajectory
'path of a projectile' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trajectory that I've seen before include "Path of a bullet or missile" , "Track of a projectile" , "Path of a projectile" , "Projectile's path" , "Path of an object through the air" .)