The most common and most likely answer to this crossword clue is the 6 plus 3 letter word BRAZIL NUT
I've seen this crossword clue in The Daily Telegraph
B
R
A
Z
I
L
N
U
T
More clues leading to the result BRAZIL NUT
- Third of puzzle to fill in brutal cryptic that's hard to crack?
- At last, green tailless lizard found in bath coming up for a nibble
- Working tribunal to protect Zulu cash crop
- Seed? Queen Elizabeth recalled end of garden, entering objection
- Fruit cups Elizabeth returned with loaf
- Last character in tribunal misrepresented, is that hard to swallow?
- One’s mad for Rio fruit
- British teachers acquiring a Russian car to get snack?
- Seed bun with filling of slaw and Ritz crackers
Buddy explains!

The straight part
We know that "snack" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case snack = brazil nut.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.