The most common and most likely answer to this crossword clue is the 9 letter word HIGH-FIVE
I've seen this crossword clue in The Times
H
I
G
H
-
F
I
V
E
Buddy explains!
The straight part
We know that "Greeting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case greeting = high-five.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 HIGH-FIVE mean?
HIGH-FIVE noun- A gesture of celebration or victory in which two people slap their hands together at shoulder height or higher.
- The game of cinch.
- To slap high fives.