The most common and most likely answer to this crossword clue is the 5 plus 3 plus 6 letter word CLOAK AND DAGGER
C
L
O
A
K
A
N
D
D
A
G
G
E
R
Buddy explains!

The straight part
We know that "Secretive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case secretive = cloak and dagger.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 CLOAK AND DAGGER mean?
CLOAK AND DAGGER adjective- Marked by menacing furtive secrecy, often with a melodramatic tint or espionage involved.