The most common and most likely answer to this crossword clue is the 7 letter word TWEETED
T
W
E
E
T
E
D
Buddy explains!

The straight part
We know that "Made a posting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case made a posting = tweeted.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 TWEETED mean?
TWEETED verb- To make a short high-pitched sound, like that of certain birds.
- To post an update to Twitter.