The most common and most likely answer to this crossword clue is the 9 letter word LITURGIST
I've seen this crossword clue in The Daily Telegraph
L
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T
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R
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Buddy explains!

The straight part
We know that "Performer of ritual" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case performer of ritual = liturgist.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 LITURGIST mean?
LITURGIST noun- A person knowledgable about liturgy.
- One who leads public worship.
- One who adheres to liturgies.