Powder found in metal container (4)
I believe the answer is:
talc
'powder' is the definition.
(I know that talc is a kind of powder)
'in metal container' is the wordplay.
'in' indicates a hidden word.
'TALC' is hidden in the letters of 'metal container'.
'found' acts as a link.
(Other definitions for talc that I've seen before include "It is used to absorb moisture" , "Fine powder" , "Softest substance in Mohs scale of hardness" , "After-bath powder" , "Cosmetic powder" .)