Dumbfound in a puzzle (5)
I believe the answer is:
'dumbfound' is the definition.
(I know that dumbfound can be written as amaze)
'a puzzle' is the wordplay.
'puzzle' becomes 'maze' (maze can mean a puzzling situation).
'in' is the link.
(Other definitions for amaze that I've seen before include "Greatly surprise in a labyrinth" , "Dumbfound" , "Greatly surprise, fill with wonder" , "Bewilder" , "Cause wonder" .)