Planet beyond Saturn (6)
I believe the answer is:
uranus
'planet beyond saturn' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for uranus that I've seen before include "Greek god ruler of universe, or a major planet" , "Might USA run up the planet?" , "Planet discovered by William Herschell in 1781" , "space traveller" , "Seventh planet from the sun" .)