The most common and most likely answer to this crossword clue is the 5 plus 6 plus 3 letter word GREAT HORNED OWL
I've seen this crossword clue in The Guardian
G
R
E
A
T
H
O
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N
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D
O
W
L
More clues leading to the result GREAT HORNED OWL
Buddy explains!
The straight part
We know that "Flying down, missing nothing? Large hooter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flying down, missing nothing? large hooter = great horned owl.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.