Assumed to be tedious person (4)
I believe the answer is:
bore
I believe this is a double definition.
'assumed' is the first definition.
(bear can mean to assume or take on)
'tedious person' is the second definition.
(I've seen this before)
'to be' acts as a link.
(Other definitions for bore that I've seen before include "Hollow out; dull person" , "hole > not something of interest" , "Dull person; tidal wave" , "Dull person; hole" , "pain from > drill" .)