A current safety device (4)
I believe the answer is:
fuse
This clue could be a double definition.
'a current safety' is the first definition.
'fuse' can be an answer for 'safety' (thesaurus). I am not certain of 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" .)