Cover the skin (4)
I believe the answer is:
hide
I believe this is a double definition.
'cover' is the first definition.
(hide is a kind of cover)
'skin' is the second definition.
(hide is a kind of skin)
'the' acts as a link.
(Other definitions for hide that I've seen before include "mask" , "A flower; an instrument" , "Not show" , "Keep under wraps" , "Once told, hurried < to > conceal" .)