Egg-shaped egg, empty (5)
I believe the answer is:
ovoid
'egg-shaped' is the definition.
('ovoid' can be a synonym of 'egg-shaped')
'egg empty' is the wordplay.
'egg' becomes 'o' (I've seen this in other clues).
'empty' becomes 'void' ('void' can be a synonym of 'empty').
'o'+'void'='OVOID'
(Other definitions for ovoid that I've seen before include "Rounded like an egg" , "Shaped like an egg" , "More or less egg-shaped" , "rounded shape" , "Like Humpty-Dumpty" .)