Previously mentioned ideas for a novel (9)
I believe the answer is:
aforesaid
'previously mentioned' is the definition.
(I've seen this before)
'ideas for a novel' is the wordplay.
'novel' indicates an anagram.
'ideas'+'for'+'a'='ideasfora'
'ideasfora' with letters rearranged gives 'AFORESAID'.
(Other definitions for aforesaid that I've seen before include "Above-mentioned" , "earlier" , "previously referred to" , "The one previously mentioned" .)