Stops working when endless stress seems terrible (5)

I believe the answer is:

rests

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'stops working' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for rests that I've seen before include "Relaxes, sleeps" , "Takes one's ease" , "Pauses; relaxes" , "holidays" , "Musical pauses" .)

I've seen this clue in the Evening Standard.

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