Orbital shape (7)
I believe the answer is:
ellipse
'orbital shape' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ellipse that I've seen before include "Geometrical oval" , "Figure like flattened circle" , "See pill (anag) - oval" , "Sell pie off for a geometric figure" , "Inclined plane through a cone" .)