The most common and most likely answer to this crossword clue is the 16 letter word NUMBER-CRUNCHING
I've seen this crossword clue in The Times
N
U
M
B
E
R
-
C
R
U
N
C
H
I
N
G
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.