The most common and most likely answer to this crossword clue is the 9 letter word PROSECUTE
I've seen this crossword clue in Independent
P
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More clues leading to the result PROSECUTE
- Engage in writing of twee character
- Sue’s dull discourse, clever
- At sea, repose around dock, or put into dock
- Try for decrease in bishop’s area of responsibility
- Multi-faceted dons exercise and do legal work
- Top of pretty flower given to pretty Sue
- Practise plain writing before appealing
- Practise with Sue
- Sue starts to party early, imbibing wine with Nick
- Plain speech on appealing charge
Buddy explains!

The straight part
We know that "Practise/Sue" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case practise/sue = prosecute.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 PROSECUTE mean?
PROSECUTE verb- To start criminal proceedings against.
- To charge, try.
- To seek to obtain by legal process.
- To pursue something to the end.