The most common and most likely answer to this crossword clue is the 9 letter word DOUBLETON
D
O
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T
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More clues leading to the result DOUBLETON
Buddy explains!

The straight part
We know that "King and queen, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case king and queen, say = doubleton.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 DOUBLETON mean?
DOUBLETON noun- A set containing precisely two elements.
- A pair of cards of the same suit, which are the only cards of that suit in a player's hand