The most common and most likely answer to this crossword clue is the 4 letter word KHAN
I've seen this crossword clue in The Times
K
H
A
N
More clues leading to the result KHAN
- Extremely knavish, authoritarian old Turkic ruler
- Old ruler shook hands, disappearing outside
- Respectful title all leaders in Karachi have adopted naturally
- Prince cross with switching of parts
- Dirkpulling jar in eastern inn
- SF film villain: King taking on Solo?
- Ruler kept hounds at Nantwich, originally
- Asian chief within shook hands
- Hong Kong upset by an Asian leader
- Some dark, handsome ruler in the East
Buddy explains!

The straight part
We know that "old Turkic ruler" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old turkic ruler = khan.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 KHAN mean?
KHAN noun- A ruler over various Turkish, Tatar and Mongol peoples in the Middle Ages.
- An Ottoman sultan.
- A noble or man of rank in various Muslim countries of Central Asia, including Afghanistan.
- A caravanserai; a resting-place for a travelling caravan.