Like an egg, to be concise (10)
I believe the answer is:
elliptical
'concise' is the definition.
(similar in meaning)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for elliptical that I've seen before include "Oval" , "description of nightmarish billiard balls?" , "regarding the motion of planets" , "Shaped like an 0" , "Obscure" .)