Fly ball's path (3)
I believe the answer is:
arc
'fly ball's path' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arc that I've seen before include "Part of circle; discharge" , "Portion of a circle" , "Luminous electrical discharge" , "Section of circumference" , "Segment of circumference" .)