The most common and most likely answer to this crossword clue is the 6 plus 5 letter word WISDOM TOOTH
I've seen this crossword clue in The Times
W
I
S
D
O
M
T
O
O
T
H
Buddy explains!
The straight part
We know that "A chopper with a delayed time of arrival" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a chopper with a delayed time of arrival = wisdom tooth.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.