The most common and most likely answer to this crossword clue is the 9 letter word NOTATIONS
N
O
T
A
T
I
O
N
S
Buddy explains!

The straight part
We know that "Symbols" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case symbols = notations.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.
What does NOTATIONS mean?
NOTATIONS noun- The act, process, method, or an instance of representing by a system or set of marks, signs, figures, or characters.
- A system of characters, symbols, or abbreviated expressions used in an art or science or in mathematics or logic to express technical facts or quantities.
- A specific note or piece of information written in such a notation.