Interrupt to cause alarm (7)
I believe the answer is:
disturb
This clue is a double definition.
'interrupt' is the first definition.
(synonyms)
'alarm' is the second definition.
(thesaurus)
'to cause' acts as a link.
(Other definitions for disturb that I've seen before include "Agitate - ruffle - trouble" , "Break" , "Trouble - interrupt" , "Upset, confuse" , "startle" .)