Superb brain - till drunk (9)
I believe the answer is:
brilliant
'superb' is the definition.
(thesaurus)
'brain till drunk' is the wordplay.
'drunk' indicates an anagram.
'brain'+'till'='braintill'
'braintill' with letters rearranged gives 'BRILLIANT'.
(Other definitions for brilliant that I've seen before include "Excellent; a diamond" , "Brainy" , "Exceptionally clever" , "Great" , "Small type" .)