The most common and most likely answer to this crossword clue is the 9 letter word MAHARISHI
I've seen this crossword clue in The Times
M
A
H
A
R
I
S
H
I
More clues leading to the result MAHARISHI
- Graduate severe about one current leading teacher
- Sharia foremost for haji in Mecca? Out of order for a Hindu
- Sage old lady, stern, embraces one upright character
- Teacher is welcome after parent, endlessly strict
- Thankless spy and head of security greeting teacher
- Teacher back in classroom? I see teacher returning greeting
- Mike has hair styled by one wise man
- Teacher raised actor and a chancellor
- Hindu instructor – mother cut his hair
- Ashram is initially tidied up to welcome spiritual leader
Buddy explains!

The straight part
We know that "leading teacher" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leading teacher = maharishi.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 MAHARISHI mean?
MAHARISHI noun- A teacher of Hindu mysticism