Definitions:
join or blend to form a single entity

(of an electrical appliance) stop working when a fuse melts

provide (a circuit or electrical appliance) with a fuse

a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.

a length of material along which a small flame moves to explode a bomb or firework, meanwhile allowing time for those who light it to move to a safe distance

fit a fuse to (a bomb, shell, or mine)