The most common and most likely answer to this crossword clue is the 6 letter word YIPPEE
I've seen this crossword clue in Financial Times
Y
I
P
P
E
E
More clues leading to the result YIPPEE
- Current Oxford course taken in six months? That's wonderful!
- Year One’s protective equipment here finally, hooray!
- Expression of delight finally, pay one penny to go
- You must restrain little kid, not the first or last to give shout of excitement
- Yep, pie’s cooked — hurray!
- Pipe circulating in the ancient expression of celebration
- Cry of joy for you harbouring giver of gratuity without any limit
- We are delighted to find ground pipe you once covered
Buddy explains!

The straight part
We know that "We are delighted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case we are delighted = yippee.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 YIPPEE mean?
YIPPEE interjection- Used to express joy or elation.