Raid carried out by old medium (5)
I believe the answer is:
radio
'medium' is the definition.
(I have seen 'Electronic medium ' mean 'radio' so perhaps 'medium' could also mean 'radio')
'raid carried out by old' is the wordplay.
'carried out' indicates an anagram (letters carried to different places).
'by' is a charade indicator (letters next to each other).
'old' becomes 'o' (abbreviation).
'raid' with letters rearranged gives 'radi'.
'radi'+'o'='RADIO'
(Other definitions for radio that I've seen before include "Contact" , "Speech receiver" , "Broadcast medium" , "Sound broadcasting" , "means of communication" .)