Ditch solving Sudoku — all real silly in the end (5)
I believe the answer is:
gully
'ditch' is the definition.
(type of artificial ditch)
'solving sudoku all real silly in the end' is the wordplay.
'in the end' says to take the final letters.
The final letters of 'solving sudoku all real silly' are 'GULLY'.
(Other definitions for gully that I've seen before include "one in the field" , "Fielding position -- narrow channel" , "Cricket fielding position" , "Narrow channel - fieldsman" , "Drain, cricket position" .)