The most common and most likely answer to this crossword clue is the 11 letter word HANG-GLIDER
I've seen this crossword clue in Financial Times
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More clues leading to the result HANG-GLIDER
Buddy explains!
The straight part
We know that "High dangler nervously losing height?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case high dangler nervously losing height? = hang-glider.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 HANG-GLIDER mean?
HANG-GLIDER noun- An unpowered aircraft resembling a large kite from which a rider is suspended in a harness.
- The rider of such a craft.