The most common and most likely answer to this crossword clue is the 6 letter word PARAPH
I've seen this crossword clue in The Times
P
A
R
A
P
H
More clues leading to the result PARAPH
Buddy explains!
The straight part
We know that "Flourish" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flourish = paraph.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 PARAPH mean?
PARAPH noun- A flourish made after or below one's signature, originally to prevent forgery.
- A mark used by medieval rubricators to indicate textual division.
- To add a paraph to; to sign, especially with one's initials.