One brought back to earth after Sun's character assassination (7)
I believe the answer is:
slander
'character assassination' is the definition.
(character assassination can mean slander)
'one brought back to earth after sun's' is the wordplay.
'one brought back to earth' becomes 'lander' (space vehicle landing back on Earth).
'after' is a charade indicator (letters next to each other).
'sun' becomes 'S' (abbreviation).
'lander' put after 's' is 'SLANDER'.
(Other definitions for slander that I've seen before include "Snarled about malicious statement" , "Injurious defamation by spoken words" , "Sling mud at" , "False or malicious report" , "Malicious speech" .)