The most common and most likely answer to this crossword clue is the 6 plus 11 plus 1 plus 7 letter word DOCTOR LIVINGSTONE I PRESUME
I've seen this crossword clue in The Guardian
D
O
C
T
O
R
L
I
V
I
N
G
S
T
O
N
E
I
P
R
E
S
U
M
E
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.