The most common and most likely answer to this crossword clue is the 11 plus 4 letter word BEST-BEFORE DATE
I've seen this crossword clue in The Times
B
E
S
T
-
B
E
F
O
R
E
D
A
T
E
More clues leading to the result BEST-BEFORE DATE
Buddy explains!
The straight part
We know that "Advice on food" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case advice on food = best-before date.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.