The most common and most likely answer to this crossword clue is the 12 letter word STUBB(ORN)LY
I've seen this crossword clue in The Guardian
S
T
U
B
B
(
O
R
N
)
L
Y
Buddy explains!
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 STUBB(ORN)LY mean?
STUBB(ORN)LY adverb- In a stubborn manner.