A worn radio receiver (7)
I believe the answer is:
bleeper
'radio receiver' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'a worn' is the wordplay.
I cannot quite see how this works, but
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found in the answer.
The remaining letters 'blee' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bleeper that I've seen before include "Electronic alert device" , "Electronic pager" , "Electronic warning device" , "Paging device" , "Small electronic device that signals the carrier" .)