Motionless form of electricity (6)
I believe the answer is:
static
This clue could be a double definition.
'motionless' is the first definition.
(synonyms)
'form of electricity' is the second definition.
'static' can be an answer for 'electricity' (static electricity is a kind of electricity). I'm not sure about the 'form of' bit.
Can you help me to learn more?
(Other definitions for static that I've seen before include "Stuck in a traffic jam" , "Not moving, like some electricity" , "Still, not moving" , "Inactive or inert" , "Noise caused by electrical interferance" .)