Planet: go beyond it (6)
I believe the answer is:
saturn
'planet' is the definition.
(Saturn is an example)
'go beyond it' is the wordplay.
'go' becomes 'turn' (as in one's go or turn in a game).
'beyond' means one lot of letters go next to another.
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'turn' put after 'sa' is 'SATURN'.
(Other definitions for saturn that I've seen before include "Giant planet" , "tried to pass vessel" , "deity" , "One of the 1 across" , "Turn as a planet" .)