The most common and most likely answer to this crossword clue is the 7 letter word PHARAOH
I've seen this crossword clue in Financial Times
P
H
A
R
A
O
H
More clues leading to the result PHARAOH
- Old king - just, we hear, and opposing harshness first of all
- Previous Egyptian spy that Iran got the covers off
- King Henry having an artist over in boozer
- Old king – just character, might you say?
- Ah Harpo! Possibly one of the greats of yesteryear
- Ancient king at pub — one with real ale on hand, for starters
- Old Egyptian gambling game, it’s said
- ‘Just use the oars’, as said by some ruler once
- Husband held by soldier: gosh mummy!
- Old King, a King enthralled by power and sudden pronouncements
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 = pharaoh.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 PHARAOH mean?
PHARAOH noun- The supreme ruler of Ancient Egypt; a formal address for the sovereign seat of power as personified by the 'king' in an institutional role of Horus son of Osiris; often used by metonymy for Ancient Egyptian sovereignty
- The card game faro.