Smooth; element (4)
I believe the answer is:
iron
I believe this is a double definition.
'smooth' is the first definition.
(to smooth down with an iron)
'element' is the second definition.
(I know that iron is a type of metal)
(Other definitions for iron that I've seen before include "inflexible > club" , "Smoother - metal" , "Smooth things" , "Metal (that may be wrought)" , "A magnet attracts it" .)