Voice disagreement after brief collapse (8)
I believe the answer is:
falsetto
'voice' is the definition.
(falsetto is a kind of voice)
'disagreement after brief collapse' is the wordplay.
'disagreement' becomes 'setto' (a 'set to' is an argument).
'after' says to put letters next to each other.
'brief' means to remove the last letter.
'collapse' becomes 'fall' (I've seen this before).
'fall' with its final letter taken off is 'fal'.
'setto' put after 'fal' is 'FALSETTO'.
(Other definitions for falsetto that I've seen before include "Unusually pitched" , "High-pitched voice above natural range" , "high notes?" , "Aritifical upper register of male voice" , "Artificial upper register of a male voice" .)