Mask and whip (4)
I believe the answer is:
hide
I believe this clue is a double definition.
'mask' is the first definition.
(both can mean to conceal or cover up)
'whip' is the second definition.
(e.g. in given a good hiding)
'and' acts as a link.
(Other definitions for hide that I've seen before include "Keep out of sight" , "Shelter" , "Animal retreat" , "Conceal with leather" , "mask" .)