The most common and most likely answer to this crossword clue is the 6 letter word SUDOKU
I've seen this crossword clue in The Guardian
S
U
D
O
K
U
More clues leading to the result SUDOKU
- Puzzle sounds oddly fair, initially unsolved
- Taking flight from here to America, about to tackle a grid-filling problem
- . Something puzzling about United Kingdom displacing old during withdrawal
- Heard solver initially gets kudos, cracking puzzle
- Having admitted affair, those in special relationship knocked over in boxing challenge?
- Kudos: you finally decoded puzzle
- Puzzling form on the upturn, United knocked us out
- Kudos built on university logic puzzle
- Upstanding partners in supposed special relationship about to complete puzzle
- Kudos! You finally solved a puzzle
Buddy explains!

The straight part
We know that "a puzzle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a puzzle = sudoku.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 SUDOKU mean?
SUDOKU noun- (games, puzzles) A type of puzzle whose completion requires each of typically nine rows and columns and each of as many usually square subregions to contain, without duplication, the digits from 1 to 9 (or the grid dimension).