Puzzle French bridge player with fine bluff, essentially (6)
I believe the answer is:
sudoku
'puzzle' is the definition.
(I've seen this before)
'french bridge player with fine bluff essentially' is the wordplay.
'french bridge player' becomes 'sud' ('south' in French - bridge players are directions).
'with' means one lot of letters go next to another.
'fine' becomes 'ok' ('OK' can be a synonym of 'fine').
'essentially' means to look at the middle letters.
The centre of 'bluff' is 'u'.
'sud'+'ok'+'u'='SUDOKU'
(Other definitions for sudoku that I've seen before include "Numerical puzzle" , "Numbers game" , "Number placement puzzle with a 9 x 9 grid" , "(Usually) nine-by-nine numbers puzzle" , "9 x 9, 1-9 puzzle" .)