Interference caused by a nervous reaction on the way (6)
I believe the answer is:
static
'interference' is the definition.
(static is a kind of interference)
'a nervous reaction on the way' is the wordplay.
'nervous reaction' becomes 'tic' (I've seen this in other clues).
'on' means one lot of letters go next to another.
'the way' becomes 'st'.
'a'+'tic'='atic'
'atic' put after 'st' is 'STATIC'.
'caused by' acts as a link.
(Other definitions for static that I've seen before include "Crackling or hissing noise caused by electrical interference" , "disturbing thing" , "Unmoving like kind of electricity" , "Inert, motionless" , "Still, not moving" .)