Real gold in addition to this unfinished check (9)
I believe the answer is:
authentic
'real' is the definition.
(I've seen this before)
'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 believe this answer much more).
'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" .)