The most common and most likely answer to this crossword clue is the 5 letter word SHEIK
I've seen this crossword clue in The Times
S
H
E
I
K
Buddy explains!
The straight part
We know that "king" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case king = sheik.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 SHEIK mean?
SHEIK noun- The leader of an Arab village, family or small tribe.
- An Islamic religious cleric; the leader of an Islamic religious order.
- (some Arab Gulf countries) An official title for members of the royal family as well as some prominent families.
- (1920s) A romantic lover. (from the 1921 film The Sheik)
- An Arab, especially one dressed in traditional clothing.
- An honorific for specialists in spirituality.