The most common and most likely answer to this crossword clue is the 7 letter word MISTERM
I've seen this crossword clue in Financial Times
M
I
S
T
E
R
M
More clues leading to the result MISTERM
Buddy explains!

The straight part
We know that "Give wrong title for Judi Dench as head spy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case give wrong title for judi dench as head spy = misterm.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.