The most common and most likely answer to this crossword clue is the 4 plus 4 letter word MATA HARI
I've seen this crossword clue in Financial Times
M
A
T
A
H
A
R
I
More clues leading to the result MATA HARI
- American subject not entirely uninteresting, having embraced a spy
- Dancing femme fatale that did harm essentially
- Receding hair, a hat, a muffler: disguise for spy
- Spy husband in Paris securing a revolutionary role
- Spy network endlessly stifling triumphant outburst
- Mother Teresa evacuated hospital — air disturbed Dutch courtesan
- Dancer has a hat perched up on untidy hair
- Spy Indian princess rejecting article without thanks
Buddy explains!
The straight part
We know that "spy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spy = mata hari.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.