Conceal the skin (4)
I believe the answer is:
hide
I believe this clue is a double definition.
'conceal' is the first definition.
(I know that conceal can be written as hide)
'skin' is the second definition.
(I know that skin can be written as hide)
'the' acts as a link.
(Other definitions for hide that I've seen before include "Animal's tough skin" , "Conceal - skin" , "Mammal's tough skin" , "(Place of) conceal(ment)" , "Keep out of sight" .)