The most common and most likely answer to this crossword clue is the 7 plus 8 letter word HOT-AIR BALLOONS
I've seen this crossword clue in Financial Times
H
O
T
-
A
I
R
B
A
L
L
O
O
N
S
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 = hot-air balloons.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.