The most common and most likely answer to this crossword clue is the 8 letter word BLUEBIRD
I've seen this crossword clue in The Daily Telegraph
B
L
U
E
B
I
R
D
Buddy explains!
The straight part
We know that "Down flier?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case down flier? = bluebird.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 BLUEBIRD mean?
BLUEBIRD noun- Any of various North American birds of the genus Sialia in the thrush family. Their plumage is blue or blue and red.
- Any of various African starlings of the genus Lamprotornis, family Sturnidae, having predominantly glossy blue plumage.