The most common and most likely answer to this crossword clue is the 3 plus 3 plus 2 plus 3 plus 3 letter word OLD MAN OF THE SEA
I've seen this crossword clue in The Daily Telegraph
O
L
D
M
A
N
O
F
T
H
E
S
E
A
More clues leading to the result OLD MAN OF THE SEA
Buddy explains!
The straight part
We know that "Unwelcome hanger-on in Arabian legend" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unwelcome hanger-on in arabian legend = old man of the sea.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.