Bad idea so far, as previously mentioned (9)
I believe the answer is:
aforesaid
'previously mentioned' is the definition.
(I've seen this before)
'bad idea so far' is the wordplay.
'bad' is an anagram indicator.
'idea'+'so'+'far'='ideasofar'
'ideasofar' anagrammed gives 'AFORESAID'.
'as' is the link.
(Other definitions for aforesaid that I've seen before include "earlier" , "previously referred to" , "The one previously mentioned" , "Above-mentioned" .)