The most common and most likely answer to this crossword clue is the 14 letter word SCHOOLMISTRESS
I've seen this crossword clue in The Sunday Telegraph
S
C
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S
More clues leading to the result SCHOOLMISTRESS
- Teacher takes train, overcoming motorway tension
- Teacher in coach overcoming motorway tension
- In middle of lesson she’s trim and cool, moving about
- Teacher in coach — note tension
- No answer in classroom? It’s she that’s upset
- A lot of swimmers I put under pressure, including male or female teacher
- She might take form displayed in Cosmo, shirtless
- Teacher to train the beloved
Buddy explains!

The straight part
We know that "female teacher" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case female teacher = schoolmistress.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 SCHOOLMISTRESS mean?
SCHOOLMISTRESS noun- A woman in charge of a school.