Shape of many racetracks (4)
I believe the answer is:
'shape of many racetracks' 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 "Egg-shaped - cricket ground" , "Shaped like an egg" , "Geometric shape" , "London cricket-ground" , "Elliptical - cricket ground" .)