The most common and most likely answer to this crossword clue is the 8 letter word PARASITE
I've seen this crossword clue in The Daily Telegraph
P
A
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A
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More clues leading to the result PARASITE
- Hanger-on in airborne soldiers’ base?
- Short piece of writing with plot gets a tick?
- Drone in place of airborne soldiers?
- Parties disrupted when gatecrashed by a hanger-on
- Around area a priest gathered mistletoe for one
- Level an area for building? It depends
- Beneath airborne soldier, spot a drone?
- Hanger-on in airborne soldier's base?
- Hanger-on, where jumping soldiers found?
- Scrounger's location beyond usual area
Buddy explains!

The straight part
We know that "a hanger-on" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a hanger-on = parasite.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 PARASITE mean?
PARASITE noun- A person who lives on other people's efforts or expense and gives little or nothing back.
- A sycophant or hanger-on.
- An organism that lives on or in another organism of a different species, deriving benefit from living on or in that other organism, while not contributing towards that other organism sufficiently to cover the cost to that other organism.
- A climbing plant which is supported by a wall, trellis etc.
- A retainer or companion of an ancient Celtic warrior, who praised him in song or poetry at gatherings; a bard.