Song in concert, unexceptional (4)
I believe the answer is:
tune
'song' is the definition.
(I've seen this before)
'in concert unexceptional' is the wordplay.
'in' indicates a hidden word.
'TUNE' is hidden in the letters of 'concert unexceptional'.
(Other definitions for tune that I've seen before include "Of engine, adjust to run smoothly" , "Air, melody" , "temper" , "Adjust for better performance" , "Adjust (car engine); air" .)