Crossword Genius

Sparks off jumper perhaps, not mobile (6)

Ross

I believe the answer is:

static

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'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" .)

I've seen this clue in The Independent.
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