The most common and most likely answer to this crossword clue is the 9 letter word NUT-BROWN
I've seen this crossword clue in Financial Times
N
U
T
-
B
R
O
W
N
More clues leading to the result NUT-BROWN
Buddy explains!
The straight part
We know that "Brunette" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case brunette = nut-brown.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 NUT-BROWN mean?
NUT-BROWN adjective- Brown as a ripe and dried nut.