Alarm rattles disturb (7)
I believe the answer is:
startle
'alarm' is the definition.
(I've seen this before)
'rattles disturb' is the wordplay.
'disturb' indicates anagramming the letters (I've seen 'disturbing' mean this).
'rattles' with letters rearranged gives 'STARTLE'.
(Other definitions for startle that I've seen before include "Rock" , "Cause to feel sudden alarm" , "Shock, alarm" , "Alarm (someone)" , "Cause to jump" .)