The most common and most likely answer to this crossword clue is the 9 letter word DO-GOODER
I've seen this crossword clue in The Guardian
D
O
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G
O
O
D
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R
Buddy explains!
The straight part
We know that "One’s always helping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one’s always helping = do-gooder.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 DO-GOODER mean?
DO-GOODER noun- One who advocates a certain course of action, often of political or social concern, with the naive conviction of their own moral superiority.