The most common and most likely answer to this crossword clue is the 3 plus 3 plus 2 plus 6 letter word OUR MAN IN HAVANA
O
U
R
M
A
N
I
N
H
A
V
A
N
A
More clues leading to the result OUR MAN IN HAVANA
Buddy explains!
The straight part
We know that "book" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case book = our man in havana.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.