Obscure novel tried once (9)
I believe the answer is:
recondite
'obscure' is the definition.
('recondite' can be a synonym of 'obscure')
'novel tried once' is the wordplay.
'novel' indicates anagramming the letters.
'tried'+'once'='triedonce'
'triedonce' anagrammed gives 'RECONDITE'.
(Other definitions for recondite that I've seen before include "Enigmatic" , "Direct one to be obscure or difficult" , "not widely known" , "Difficult to understand" , "Abstruse" .)