Brave choir performed with energy (6)
I believe the answer is:
heroic
'brave' is the definition.
(I've seen this in another clue)
'choir performed with energy' is the wordplay.
'performed with' indicates an anagram.
'energy' becomes 'e' (physics symbol as in E=mc2).
'choir' mixed up with 'e' gives 'HEROIC'.
(Other definitions for heroic that I've seen before include "Surpassing the ordinary, in courage say" , "Showing extreme courage" , "Very brave and noble" , "Epic" , "Dramatic" .)