The most common and most likely answer to this crossword clue is the 4 letter word WHEE
I've seen this crossword clue in The Times
W
H
E
E
More clues leading to the result WHEE
- Here we go — breathing with difficulty, lacking energy
- Turn left? No, this is fun
- Shriek of excitement as new driver fails to make turn
- Turner’s short expression of excitement
- Primarily, word hollered exhibiting exuberance?
- Go by bike, covering length – yay!
- That’s exciting early invention left abandoned
- That’s exciting turn that shouldn’t finish!
- I’m thrilled revolver’s left unfinished
- It reveals excitement as we pick up ambassador
Buddy explains!

The straight part
We know that "expression of excitement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case expression of excitement = whee.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 WHEE mean?
WHEE interjection- An expression of pleasure or enjoyment, mostly from rapid physical motion.