Shape of a 0 (4)
I believe the answer is:
oval
'shape of a 0' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oval that I've seen before include "Stretched circle?" , "Cricket ground - presidential office" , "Egg shape, roughly" , "Race track" , "Elliptical - cricket ground" .)