Pierce is tedious person (4)
I believe the answer is:
bore
I believe this clue is a double definition.
'pierce' is the first definition.
(thesaurus)
'tedious person' is the second definition.
(I've seen this in another clue)
'is' is the link.
(Other definitions for bore that I've seen before include "Weary with tediousness" , "Drill to be tiresome" , "Hollow barrel" , "Tidal wave; drill" , "Dull person; use a drill" .)