Message received, man! (5)
I believe the answer is:
roger
This clue is a double definition.
'message received' is the first definition.
(I've seen this before)
'man' is the second definition.
(I've seen this before)
(Other definitions for roger that I've seen before include "Message received and understood!" , "Boy's name - received and understood" , "Chap" , "I have heard on the radio" , "Message received; name" .)