Sparks off jumper perhaps, not mobile (6)
I believe the answer is:
static
'mobile' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for static that I've seen before include "stable" , "Not moving - electrical interference" , "showing no signs of going anywhere" , "Crackling or hissing noise caused by electrical interference" , "Still, not moving" .)