Powder in metal containers (4)
I believe the answer is:
talc
'powder' is the definition.
(talcing is a kind of powdering)
'in metal containers' is the wordplay.
'in' says the answer is hidden in the clue.
'TALC' is hidden within 'metal containers'.
(Other definitions for talc that I've seen before include "Mineral used as a toiletry" , "Cosmetic powder" , "Perfumed drying powder" , "It is used to absorb moisture" , "Toilet powder - mica" .)