Succeeded with a fit, heavenly body (6)
I believe the answer is:
saturn
'heavenly body' is the definition.
(Saturn is an example)
'succeeded with a fit' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'with' says to put letters next to each other.
'fit' becomes 'turn' (I've seen this before).
's'+'a'+'turn'='SATURN'
(Other definitions for saturn that I've seen before include "Titan its moon" , "orbits the sun" , "Sixth rock from the sun" , "Solar system planet" , "Planet with concentric rings" .)