Declines to change? Shut up! (8)
I believe the answer is:
silenced
'shut up' is the definition.
(I've seen this in another clue)
'declines to change?' is the wordplay.
'to change?' is an anagram indicator (I've seen 'to change' mean this).
'declines' with letters rearranged gives 'SILENCED'.
(Other definitions for silenced that I've seen before include "Declines to be made mute" , "Stopped from speaking" , "cut short" , "shut up" , "Declines to be made quiet" .)