The most common and most likely answer to this crossword clue is the 8 letter word WAGTAILS
I've seen this crossword clue in The Daily Telegraph
W
A
G
T
A
I
L
S
More clues leading to the result WAGTAILS
Buddy explains!
The straight part
We know that "fliers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fliers = wagtails.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 WAGTAILS mean?
WAGTAILS noun- Any of various small passerine birds of the family Motacillidae, of the Old World, notable for their long tails.