A current safety device (4)
I believe the answer is:
fuse
This might be a double definition.
'a current safety' is the first definition.
'fuse' can be an answer for 'safety' (thesaurus). I'm not sure about the 'a current' bit.
'device' is the second definition.
(fuse is a kind of device)
Can you help me to learn more?
(Other definitions for fuse that I've seen before include "Coalesce, melt together" , "Melt with heat" , "Mix together" , "Common electrical safety device in homes etc" , "Tube or cord for igniting an explosive" .)