Safety device that may be installed in a bomb (4)
I believe the answer is:
fuse
This could be a double definition.
'safety' is the first definition.
(thesaurus)
'device that may be installed in a bomb' is the second definition.
'fuse' can be an answer for 'device' (fuse is a kind of device). I'm unsure of the remainder of the definition.
Can you help me to learn more?
(Other definitions for fuse that I've seen before include "Safeguard in electrical circuit" , "Join or blend to form an entity" , "circuit-breaker" , "Tube or cord for igniting an explosive" , "Weld together through heat" .)