The most common and most likely answer to this crossword clue is the 6 letter word HUZZAH
I've seen this crossword clue in Financial Times
H
U
Z
Z
A
H
Buddy explains!
The straight part
We know that "Exclamation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case exclamation = huzzah.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 HUZZAH mean?
HUZZAH noun- A cheer often associated with sailors, shouted by a group in praise of a thing or event.
- To cheer with a huzzah sound.
- Used as a call for coordinated physical effort, as in hoisting.
- (sometimes humorous) Used as a cheer indicating exaltation, enjoyment or approval.