A ball of sorbo rubber (3)
I believe the answer is:
orb
'a ball' is the definition.
('orb' can be a synonym of 'ball')
'of sorbo rubber' is the wordplay.
'of' indicates the answer is hidden within the clue.
'ORB' is hidden in the letters of 'sorbo rubber'.
(Other definitions for orb that I've seen before include "component of royal regalia" , "Sphere for a sovereign" , "Heavenly body" , "ball with cross" , "Sphere - eye" .)