The most common and most likely answer to this crossword clue is the 4 plus 3 plus 5 letter word SAGE AND ONION
S
A
G
E
A
N
D
O
N
I
O
N
More clues leading to the result SAGE AND ONION
Buddy explains!
The straight part
We know that "seasonal ingredients" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case seasonal ingredients = sage and onion.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.