Become hostile when you start to listen to the radio (4,2)
I believe the answer is:
turn on
'radio' is the definition.
Although both the answer and definition are verbs in their base form, I don't see how one could define the other.
'become hostile when you start to listen to' is the wordplay.
I cannot quite see how this works, but
'become' could be 'turn' (synonyms) and 'turn' is located in the answer.
'when' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'the' acts as a link.
Can you help me to learn more?
(Other definitions for turn on that I've seen before include "Set in operation" , "please" , "Excite sexually" , "Start working" , "Person with twenty five [SEX APPEAL]" .)