Radio interference (6)
I believe the answer is:
static
'radio interference' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for static that I've seen before include "Changeless" , "Unmoving like kind of electricity" , "Inert or passive, like some electricity" , "Atmospheric disturbance" , "Crackling or hissing noise caused by electrical interference" .)