The most common and most likely answer to this crossword clue is the 9 letter word BADGERING
I've seen this crossword clue in The Guardian
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More clues leading to the result BADGERING
Buddy explains!

The straight part
We know that "Using repeated persuasion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case using repeated persuasion = badgering.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 BADGERING mean?
BADGERING verb- To pester, to annoy persistently; press.
- To pass gas; to fart.
- The act of one who badgers, pesters, or annoys.