Brief, wrongly maligned at first, does well currently? (9)
I believe the answer is:
misinform
'brief wrongly' is the definition.
(to misinform is to brief with wrong information)
'maligned at first does well currently?' is the wordplay.
'at first' says to take the initial letters.
'does well currently?' becomes 'isinform' ('in form' means doing well eg in sport).
The first letter of 'maligned' is 'm'.
'm'+'isinform'='MISINFORM'
(Other definitions for misinform that I've seen before include "Deceive" , "Instruct wrongly" , "Wrongly teach" , "Wrongly advise" , "Give inaccurate info to (someone)" .)