The most common and most likely answer to this crossword clue is the 10 letter word CATECHISED
I've seen this crossword clue in The Times
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Buddy explains!
The straight part
We know that "questioned systematically" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case questioned systematically = catechised.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 CATECHISED mean?
CATECHISED verb- To give oral instruction, especially of religion; now specifically by the formal question-and-answer method; in the Church of England, to teach the catechism as preparation for confirmation.
- To question at length.