Writer one associates with Notts Forest (9)
I believe the answer is:
isherwood
'writer' is the definition.
(I know that Isherwood is a writer)
'one associates with notts forest' is the wordplay.
'one' becomes 'i' (Roman numeral).
'associates with' means one lot of letters go next to another.
'notts' becomes 'sher' (I am not sure about this - if you are sure you should believe this answer much more).
'forest' becomes 'wood' (synonyms).
'i'+'sher'+'wood'='ISHERWOOD'
Can you help me to learn more?
(Other definitions for isherwood that I've seen before include "Christopher --, novelist (Goodbye to Berlin)" , "writer" , "Playwright" , "Christopher ---, C20 novelist" , "Author" .)