Conceal, disguise (4)
I believe the answer is:
mask
This clue is a double definition.
'conceal' is the first definition.
(I know that mask is a kind of disguise)
'disguise' is the second definition.
(I know that mask is a kind of disguise)
(Other definitions for mask that I've seen before include "Camouflage" , "Face-cover" , "Domino" , "One hiding, protecting face" , "Cover for the face" .)