The highest object of Roman worship: a large, almost spherical body (7)
I believe the answer is:
jupiter
I believe this is a double definition.
'the highest object of roman worship' is the first definition.
(Roman god)
'a large almost spherical body' is the second definition.
(as in the planet)
(Other definitions for jupiter that I've seen before include "to which Tom Towers contributed" , "Chief of the Gods, by Jove" , "Piece of Holst" , "Planet - Roman equivalent of Zeus" , "Chief Roman god" .)