Can — it reportedly contains salt (5)
I believe the answer is:
nitre
'salt' is the definition.
(nitre is a kind of salt)
'can it reportedly contains' is the wordplay.
'contains' indicates a hidden word.
'NITRE' can be found hidden inside 'can it reportedly'.
(Other definitions for nitre that I've seen before include "Mineral used in gunpowder" , "Also known as salt-petre" , "Inert kind of saltpetre" , "explosive producer?" , "Inter (anag.)" .)