The most common and most likely answer to this crossword clue is the 7 letter word SEAGULL
I've seen this crossword clue in Financial Times
S
E
A
G
U
L
L
Buddy explains!
The straight part
We know that "High-flier" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case high-flier = seagull.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 SEAGULL mean?
SEAGULL noun- Any of several white, often dark backed birds of the family Laridae having long pointed wings and short legs.
- The symbol ΜΌ , which combines under a letter as a sort of accent.
- A fan or member of Brighton and Hove Albion Football Club.
- (of a forward) To run in the back line rather than concentrate on primary positional duties in open play.
- To use a British Seagull outboard.
- To work as a non-union casual stevedore.