Escape mechanism used for shutting down quickly (4)
I believe the answer is:
bolt
'escape' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for bolt that I've seen before include "playwright" , "Latch" , "writer" , "From the blue, it's a big surprise" , "It makes fast" .)