Kudos! You finally cracked puzzle (6)
I believe the answer is:
sudoku
'puzzle' is the definition.
(I've seen this before)
'kudos you finally cracked' is the wordplay.
'you' becomes 'u' (homophones).
'finally' is a charade indicator (letters next to each other) (some letters go at the end of others).
'cracked' indicates an anagram.
'kudos'+'u'='kudosu'
'kudosu' anagrammed gives 'SUDOKU'.
(Other definitions for sudoku that I've seen before include "filling boxes" , "(Usually) nine-by-nine numbers puzzle" , "Numeric puzzle" , "Numbers game" , "Popular number puzzle" .)