Discovered in the Alhambra: Zorro's blade (5)
I believe the answer is:
razor
'blade' is the definition.
(I've seen this before)
'discovered in the alhambra zorro's' is the wordplay.
'discovered' says the answer is hidden in the clue (remove the letters covering the answer in the clue).
'RAZOR' is hidden within 'in alhambra zorros'.
(Other definitions for razor that I've seen before include "Sharp blade" , "cut-throat" , "Shaver's implement" , "It removes 2" , "Sharp implement" .)