Curves shown by Caprice so regularly (4)
I believe the answer is:
arcs
'curves' is the definition.
('arc' can be a synonym of 'curve')
'caprice so regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'caprice'+'so'='capriceso'
The alternating letters of 'capriceso' are 'ARCS'.
'shown by' acts as a link.
(Other definitions for arcs that I've seen before include "Streaks of electrical discharges" , "Curving trajectories" , "Segments of a circle" , "Portions of a circle" , "Cars (anag)" .)