Flow of electricity (7)
I believe the answer is:
current
I believe this clue is a double definition.
'flow' is the first definition.
(current is a kind of flow)
'electricity' is the second definition.
(current electricity is a kind of electricity)
'of' acts as a link.
(Other definitions for current that I've seen before include "Up-to-date" , "In general use; flow" , "Source of power" , "Flow, of a river say" , "In vogue" .)