Masquerade (as) (4)
I believe the answer is:
pose
'masquerade as' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pose that I've seen before include "Pretend to be somebody else" , "Attitude struck" , "Sit as model" , "'Present, a problem say (4)'" , "position" .)