Amaze two Zulus in valley (6)
I believe the answer is:
dazzle
'amaze' is the definition.
(I've seen this in another clue)
'two zulus in valley' is the wordplay.
'two zulus' means two substitutions for 'zulu'.
'zulu' becomes 'Z' (phonetic alphabet: alpha, bravo, charlie etc.).
'zulu' becomes 'Z' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' is an insertion indicator.
'valley' becomes 'dale' (dale is a kind of valley).
'z'+'z'='zz'
'zz' inserted within 'dale' is 'DAZZLE'.
(Other definitions for dazzle that I've seen before include "See 15" , "Temporalily blind with intense light" , "Animal's den" , "glitter" , "Blind with light or skill" .)