Return of Puck with wonderful puzzle (6)
I believe the answer is:
baffle
'puzzle' is the definition.
(baffle can mean to puzzle)
'return of puck with wonderful' is the wordplay.
'return of' says the letters should be written backwards.
'puck' becomes 'elf' (puck can mean a fairy).
'with' says to put letters next to each other.
'wonderful' becomes 'fab' (slang abbreviation of fabulous).
'elf'+'fab'='elffab'
'elffab' back-to-front is 'BAFFLE'.
(Other definitions for baffle that I've seen before include "Mystify, flummox" , "Puzzle - foil" , "Totally bewilder" , "Damper - foil" , "Mystify, bewilder" .)