Successful prose pours out (10)
I believe the answer is:
prosperous
'successful' is the definition.
(similar in meaning)
'prose pours out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'prose'+'pours'='prosepours'
'prosepours' anagrammed gives 'PROSPEROUS'.
(Other definitions for prosperous that I've seen before include "thriving" , "Rich" , "Well-to-do" , "Wealthy" , "Affluent" .)