Top Olympian jumper missing third, having crossed it (7)

I believe the answer is:

jupiter

I'm a little stuck... Click here to teach me more about this clue!

'top olympian' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for jupiter that I've seen before include "Chief Roman god" , "Planet - Roman equivalent of Zeus" , "Heavenly body" , "to which Tom Towers contributed" , "A planet; Trollope's all-powerful newspaper" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.