The most common and most likely answer to this crossword clue is the 4 letter word KITE
I've seen this crossword clue in The Sunday Telegraph
K
I
T
E
More clues leading to the result KITE
- Bird that’s flown as an experiment
- Coming from peak, it evades a bird of prey
- Hawk that is blown by the wind
- End of line attached to equipment that can fly
- Tackle English bird of prey
- Christopher E Bird
- Tackle header or footer on elaborate flyer
- Bird originally kept in tiny enclosure
- Strip and remove shell of jet plane
- Tackle English bird
Buddy explains!

The straight part
We know that "flier" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flier = kite.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.