Glass on the radio (3)
I believe the answer is:
ira
'glass on the radio' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ira that I've seen before include "terrorists" , "George 13 down's brother" , "Illegal organisation, initially" , "Songwriter George's elder brother" , "George Gershwin's older brother, the lyricist" .)