Performing together (2,7)
I believe the answer is:
in concert
I believe this clue is a double definition.
'performing' is the first definition.
(I've seen this before)
'together' is the second definition.
(I know that together can be written as in concert)
(Other definitions for in concert that I've seen before include "Acting together" , "Working together" , "Showing teamwork" , "on stage?" , "Playing live - together" .)