Cones' counterparts (4)
I believe the answer is:
rods
'cones' counterparts' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rods that I've seen before include "Thin sticks or staffs of office" , "Batons" , "Those angling" , "Biblical races" , "Straight, thin sticks" .)