Smooth learner in orchestra (5)
I believe the answer is:
bland
'smooth' is the definition.
(thesaurus)
'learner in orchestra' is the wordplay.
'learner' becomes 'l'.
'in' is an insertion indicator.
'orchestra' becomes 'band' (I've seen this before).
'l' going into 'band' is 'BLAND'.
(Other definitions for bland that I've seen before include "Insipid, vapid" , "Suave" , "Unruffled but unstimulating" , "Insipid; lacklustre" , "Lacking taste, flavour" .)