Bonus song at a concert (6)
I believe the answer is:
encore
'bonus song at a concert' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for encore that I've seen before include "Bis!" , "(Call for) repeat performance" , "Enthusiastic call" , "Audience call for another performance" , "Let's hear/see it again!" .)