The most common and most likely answer to this crossword clue is the 9 letter word STRANDING
I've seen this crossword clue in The Daily Telegraph
S
T
R
A
N
D
I
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G
More clues leading to the result STRANDING
Buddy explains!

The straight part
We know that "Leaving helpless" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leaving helpless = stranding.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 STRANDING mean?
STRANDING verb- To run aground; to beach.
- To leave (someone) in a difficult situation; to abandon or desert.
- To cause the third out of an inning to be made, leaving a runner on base.
- To break a strand of (a rope).
- To form by uniting strands.
- The act by which somebody is stranded.