Lad in charge of sound (5)
I believe the answer is:
sonic
'of sound' is the definition.
(I've seen this before)
'lad in charge' is the wordplay.
'lad' becomes 'son'.
'in charge' becomes 'ic'.
'son'+'ic'='SONIC'
(Other definitions for sonic that I've seen before include "Employing sound" , "Type of boom" , "Producing sound" , "Boom of jet aircraft" , "Travelling at Mach One" .)