Tedious person (4)
I believe the answer is:
bore
'tedious person' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bore that I've seen before include "Tidal wave; drill" , "Capable of being shifted" , "Pierce or tire with tedium" , "Drill or be tedious" , "Dull person; tidal wave" .)