The writer, in pain, read French poetry for successful people (9)
I believe the answer is:
achievers
'successful people' is the definition.
The definition and answer can be both people as well as being plural nouns.
Perhaps you can see a link between them that I can't see?
'the writer in pain read french poetry' is the wordplay.
'the writer' becomes 'I' (the person who is writing these clues).
'in' indicates putting letters inside.
'pain' becomes 'ache' (ache is a kind of pain).
'read french poetry' becomes 'vers' (I am not sure about this - if you are sure you should believe this answer much more).
'i' put within 'ache' is 'achie'.
'achie'+'vers'='ACHIEVERS'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for achievers that I've seen before include "winners" , "People who get things done" .)