The most common and most likely answer to this crossword clue is the 14 letter word FUNDAMENTALIST
I've seen this crossword clue in Independent
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Buddy explains!
The straight part
We know that "zealot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case zealot = fundamentalist.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 FUNDAMENTALIST mean?
FUNDAMENTALIST noun- One who reduces religion to strict interpretation of core or original texts.
- A trader who trades on the financial fundamentals of the companies involved, as opposed to a chartist or technician.
- Originally referred to an adherent of an American Christian movement that began as a response to the rejection of the accuracy of the Bible, the alleged deity of Christ, Christ's atonement for humanity, the virgin birth, and miracles.
- A fundamentalist Christian.