Conducted electricity activates this (3)
I believe the answer is:
led
'conducted' is the definition.
('lead' can be a synonym of 'conduct')
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for led that I've seen before include "sort of light" , "Paved the way" , "Went at the head of others" , "Was guiding" , "Shown the way" .)