The most common and most likely answer to this crossword clue is the 9 letter word FORWARDER
I've seen this crossword clue in Independent
F
O
R
W
A
R
D
E
R
More clues leading to the result FORWARDER
Buddy explains!
The straight part
We know that "Who passes on message" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who passes on message = forwarder.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does FORWARDER mean?
FORWARDER noun- One who, or that which, forwards something to another destination.