The most common and most likely answer to this crossword clue is the 5 letter word TWEET
I've seen this crossword clue in The Times
T
W
E
E
T
More clues leading to the result TWEET
- Message online and call from branch?
- Abstainer penning little message
- In races need minute to send messages
- Leaders of think tank penning little message
- Middle of battle interrupted by little message
- Message is dry with little content
- Message to take down, quickly read out?
- Communicate what means little, time after time
- Message from Times taking the piss
- Water gets into dry post
Buddy explains!

The straight part
We know that "message" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case message = tweet.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 TWEET mean?
TWEET noun- The sound of a bird; any short high-pitched sound or whistle.
- An entry posted on the microblogging service Twitter.
- To make a short high-pitched sound, like that of certain birds.
- To post an update to Twitter.
- An onomatopoeic of bird singing.