The most common and most likely answer to this crossword clue is the 7 letter word SHO’GUN
I've seen this crossword clue in The Guardian
S
H
O
â
€
™
G
U
N
Buddy explains!

The straight part
We know that "Leader" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leader = sho’gun.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 SHO’GUN mean?
SHO’GUN noun- The supreme generalissimo of feudal Japan.