Brisk musical movement (7)
I believe the answer is:
allegro
'brisk musical movement' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for allegro that I've seen before include "Gaily, lively (music)" , "quickly found in bars?" , "musical term" , "At a brisk speed (music)" , "(In music) briskly" .)