American in favour of new ideas, as previously mentioned (9)
I believe the answer is:
aforesaid
'previously mentioned' is the definition.
(I've seen this before)
'american in favour of new ideas' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'in favour' becomes 'for' (I've seen this before).
'of new' indicates anagramming the letters (I've seen 'new' mean this).
'ideas' with letters rearranged gives 'esaid'.
'a'+'for'+'esaid'='AFORESAID'
'as' is the link.
(Other definitions for aforesaid that I've seen before include "Above-mentioned" , "earlier" , "previously referred to" , "The one previously mentioned" .)