The most common and most likely answer to this crossword clue is the 6 letter word AMERCE
A
M
E
R
C
E
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The straight part
We know that "fine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fine = amerce.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 AMERCE mean?
AMERCE verb- To impose a fine on; to fine.
- To punish; to make an exaction.