Real gold in addition to this unfinished check (9)
I believe the answer is:
authentic
'real' is the definition.
(I've seen this in another clue)
'gold in addition to this unfinished check' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'in addition' becomes 'then' (I've seen this in another clue).
'to this unfinished check' becomes 'tic' (I can't justify this - if you can you should give a lot more credence to this answer).
'au'+'then'+'tic'='AUTHENTIC'
Can you help me to learn more?
(Other definitions for authentic that I've seen before include "24 [LEGIT]" , "reliable" , "Bona fide" , "trustworthy" , "Real, genuine" .)