The most common and most likely answer to this crossword clue is the 4 letter word AMOS
I've seen this crossword clue in The Guardian
A
M
O
S
More clues leading to the result AMOS
- Prophet captured by Grandma Moses
- In the morning getting bigger-than-average holy book
- I love old Italian school book
- Bookmaker heading out from Greek island
- Army doctor opening a small book
- Prophet of a second coming before end of Christmas
- A very short book
- When to be visited by flash old prophet
- Adult writing about love in book
- Intoxicating drink from the right prophet
Buddy explains!

The straight part
We know that "prophet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case prophet = amos.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.