Assume it's a hoax (3,2)
I believe the answer is:
put on
This clue is a double definition.
'assume' is the first definition.
(to put something on is to assume it)
'a hoax' is the second definition.
(I've seen this before)
'it's' acts as a link.
(Other definitions for put on that I've seen before include "Don clothes or stage play" , "Affixed" , "Increase as with weight" , "Apply (to a surface) - present (on stage)" , "Assume < present" .)