Genuine article in auction, not old, reproduced (9)
I believe the answer is:
authentic
'genuine' is the definition.
(similar in meaning)
'article in auction not old reproduced' is the wordplay.
'article' becomes 'the' (the definite article in English).
'in' indicates putting letters inside.
'not' indicates named letters should be taken away.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'reproduced' is an anagram indicator (I've seen 'reproduce' mean this).
'auction' with 'o' removed is 'auctin'.
'auctin' anagrammed gives 'auntic'.
'the' placed inside 'auntic' is 'AUTHENTIC'.
(Other definitions for authentic that I've seen before include "Real, genuine" , "24 [LEGIT]" , "trustworthy" , "Genuine, not a copy" , "Ian, the cut is genuine" .)