The most common and most likely answer to this crossword clue is the 7 plus 6 letter word MUSTARD POWDER
I've seen this crossword clue in The Guardian
M
U
S
T
A
R
D
P
O
W
D
E
R
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.