The most common and most likely answer to this crossword clue is the 10 letter word CATECHUMEN
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More clues leading to the result CATECHUMEN
Buddy explains!

The straight part
We know that "new convert" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case new convert = catechumen.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 CATECHUMEN mean?
CATECHUMEN noun- A convert to Christianity under instruction before baptism; a young or recent Christian preparing for confirmation.