Raid carried out by old medium (5)
I believe the answer is:
radio
'medium' is the definition.
(I know that radio is a type of broadcasting)
'raid carried out by old' is the wordplay.
I cannot really see how this works, but
an anagram of 'raid' is 'radi' which is within the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for radio that I've seen before include "Contact" , "Speech receiver" , "Broadcast medium" , "Sound broadcasting" , "means of communication" .)