4 across
Noise
on
the
radio
still
(6)
Noise on the radio still (6)
hints
0
checks
0
hints
The whole clue is the definition (& lit or double definition).
How the clue works
The definition is Noise on the radio, giving you that crackling interference sense of the answer. Still does double duty here as a second definition — motionless, unchanging — so the whole clue is a elegant double definition pulling the same word from two directions.