The most common and most likely answer to this crossword clue is the 7 plus 2 plus 1 plus 4 plus 4 plus 6 plus 4 letter word REVENGE IS A DISH BEST SERVED COLD
I've seen this crossword clue in The Guardian
R
E
V
E
N
G
E
I
S
A
D
I
S
H
B
E
S
T
S
E
R
V
E
D
C
O
L
D
Buddy explains!
The straight part
We know that "saying?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case saying? = revenge is a dish best served cold.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.