Twig it’s some sort of electrical device (6)
I believe the answer is:
Here is my best explanation:
'twig' is the definition.
'it's some sort of electrical device' is the wordplay.
I cannot really understand how this works, but
'it's' could be 'it' (I've seen this in other clues) and 'it' is found in the answer.
This explanation may well be incorrect...
(Other definitions for switch that I've seen before include "electrical device", "One may be off", "Change or cane", "Whip", "that turns on the power", "Substitute", "Exchange; contactor", "Device for opening and closing electric circuits", "It may be thrown" and "Change round".)