Electrically-charged particles (4)
I believe the answer is:
ions
'electrically-charged particles' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ions that I've seen before include "N in radio comms." , "items with a charge" , "Electrically-charged particles" , "Charged atom or molecule" , "Electrically charged particles" .)