Crossword Genius

Bad idea so far, as previously mentioned (9)

Ross

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" .)

I've seen this clue in The Telegraph.
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