Metal used by Heinz in cans (4)
I believe the answer is:
zinc
'metal' is the definition.
(zinc is a metal)
'used by heinz in cans' is the wordplay.
'used by' says the answer is hidden in the clue.
'ZINC' is hidden in the letters of 'heinz in cans'.
(Other definitions for zinc that I've seen before include "Blusish-white lustrous metallic element" , "Silvery-white metal" , "Component of brass" , "Sivery-white metal" , "Blue-white metallic element, atomic number 30" .)