The most common and most likely answer to this crossword clue is the 6 letter word MASHER
M
A
S
H
E
R
Buddy explains!
The straight part
We know that "a flirt" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a flirt = masher.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 MASHER mean?
MASHER noun- One who, or that which, mashes.
- A machine for making mash.
- A fashionable man in the late Victorian era.
- A man who makes often unwelcome advances to women, as in a subway.