The most common and most likely answer to this crossword clue is the 9 letter word DESIRABLE
I've seen this crossword clue in The Guardian
D
E
S
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R
A
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More clues leading to the result DESIRABLE
Buddy explains!
The straight part
We know that "Helpful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case helpful = desirable.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 DESIRABLE mean?
DESIRABLE noun- A thing that people want; something that is desirable.
- Worthy to be desired; pleasing; agreeable.