Path of a fly ball or storyline (3)
I believe the answer is:
arc
I believe this is a double definition.
'path of a fly ball' is the first definition.
(I've seen this in another clue)
'storyline' is the second definition.
(I've seen this in another clue)
(Other definitions for arc that I've seen before include "Part of a circle's circumference" , "Car (anag.)" , "A curve for Joan of . . ." , "circle, partly" , "Curve of car" .)