The most common and most likely answer to this crossword clue is the 10 letter word PROCURATOR
I've seen this crossword clue in The Times
P
R
O
C
U
R
A
T
O
R
Buddy explains!
The straight part
We know that "Expert at court regularly defending scoundrel/?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case expert at court regularly defending scoundrel/? = procurator.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 PROCURATOR mean?
PROCURATOR noun- A tax collector.
- An agent or attorney.
- A legal officer who both investigates and prosecutes crimes, found in some inquisitorial legal systems, particularly communist or formerly communist states – see public procurator
- The governor of a small imperial province.