Sets aside, it swells in sound (6)
I believe the answer is:
waives
'sets aside' is the definition.
(I've seen this in another clue)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for waives that I've seen before include "Renounces" , "Relinquishes legal claim to" , "Relinquishes a right" .)