The most common and most likely answer to this crossword clue is the 2 plus 6 letter word DO GOODER
I've seen this crossword clue in Financial Times
D
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Buddy explains!
The straight part
We know that "person trying to be virtuous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case person trying to be virtuous = 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.