Brandish loud whip (5)
I believe the answer is:
flash
'brandish' is the definition.
(I've seen this before)
'loud whip' is the wordplay.
'loud' becomes 'f' (A musical term).
'whip' becomes 'lash' ('lash' can be a synonym of 'whip').
'f'+'lash'='FLASH'
(Other definitions for flash that I've seen before include "Sudden gleam of light" , "emblem on uniform" , "Brief burst of light" , "Conspicuously display" , "Mo" .)