The most common and most likely answer to this crossword clue is the 7 letter word SPELLER
S
P
E
L
L
E
R
More clues leading to the result SPELLER
Buddy explains!

The straight part
We know that "Sorceress/who knows how many ‘s’s?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sorceress/who knows how many ‘s’s? = speller.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 SPELLER mean?
SPELLER noun- A person who spells.
- A participant in a spelling bee.
- A book used to learn how to spell properly.
- A spell checker.