Metal from Cadiz in container (4)
I believe the answer is:
zinc
'metal' is the definition.
(zinc is a metal)
'from cadiz in container' is the wordplay.
'from' indicates the answer is hidden within the clue.
'ZINC' is hidden within 'cadiz in container'.
(Other definitions for zinc that I've seen before include "Ingredient in brass" , "it might be galvanising" , "Bluish-white metal" , "Silvery-white metal" , "It is used to coat iron against corrosion" .)