The most common and most likely answer to this crossword clue is the 7 plus 6 letter word BERNARD HEPTON
I've seen this crossword clue in Financial Times
B
E
R
N
A
R
D
H
E
P
T
O
N
Buddy explains!
The straight part
We know that "Tinker, Tailor, Soldier, Spy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tinker, tailor, soldier, spy = bernard hepton.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.