The most common and most likely answer to this crossword clue is the 7 plus 6 letter word HERCULE POIROT
I've seen this crossword clue in The Daily Telegraph
H
E
R
C
U
L
E
P
O
I
R
O
T
More clues leading to the result HERCULE POIROT
- A detective, I report louche suspect
- Detective flying our helicopter
- Detective in our helicopter, squirming
- Hotel croupier misdealt to famous Belgian
- Fabled detective frisking hotel croupier
- Hire pro to broadcast about unravelling clue — him?
- Expert investigating our helicopter crashing
- Detective emerging from helicopter with our suspect
Buddy explains!
The straight part
We know that "Expert investigating" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case expert investigating = hercule poirot.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.