You finally leave sudoku undone and gain prestige (5)
I believe the answer is:
kudos
'prestige' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for kudos that I've seen before include "Pats on the back" , "Informal honour of glory" , "Renown" , "Laudation" , "Fame - prestige" .)