The most common and most likely answer to this crossword clue is the 7 letter word NYMPHET
I've seen this crossword clue in Financial Times
N
Y
M
P
H
E
T
More clues leading to the result NYMPHET
- Pen myth about sexy girl
- Variable speed in goal leads to miss after it?
- Unknown speed trap's without siren, perhaps
- Nora? Pa’s besotted with her – her antonym perhaps!
- New York representative with the novel Lolita, perhaps
- Extremely naughty congresswoman got the man spent finally - could be 16 girl
- Attractive girl's lure has stranger after it
- Speed unit stopping still – on tail of Hillman Minx?
Buddy explains!

The straight part
We know that "Minx" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case minx = nymphet.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 NYMPHET mean?
NYMPHET noun- A small nymph.
- A sexually attractive girl or young woman.