The most common and most likely answer to this crossword clue is the 7 letter word FANATIC
I've seen this crossword clue in The Daily Telegraph
F
A
N
A
T
I
C
More clues leading to the result FANATIC
- Cooler? Greek sounding enthusiastic
- One with obsession to cool attic, but only one time
- Enthusiast I dressed in flowing caftan
- Force clown to entertain American zealot
- Encourage a jerk to become extremist
- Nut cracking, in fact, absorbs one
- Obsessive American inspired by cool reaction
- Fiat can design for enthusiast
- Zealot‘s found in cooler upstairs room, disheartened
- Crazy American in fact is a zealot
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 = fanatic.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 FANATIC mean?
FANATIC noun- A person who is zealously enthusiastic for some cause, especially in religion.
- Fanatical.
- Showing evidence of possession by a god or demon; frenzied, overzealous.