Pretence or disguise (10)
I believe the answer is:
masquerade
I believe this is a double definition.
'pretence' is the first definition.
(masquerade is a kind of pretence)
'disguise' is the second definition.
(masquerading is a kind of disguising)
(Other definitions for masquerade that I've seen before include "False show - disguise oneself" , "Adam's queer? (anag)" , "Deception" , "False show; pretence" , "where everyone's wearing the veil" .)