Witness in the bishop's seat (3)
I believe the answer is:
see
I believe this is a double definition.
'witness' is the first definition.
(I know that witness is a more specific form of see)
'bishop's seat' is the second definition.
(I've seen this in another clue)
'in the' is the link.
(Other definitions for see that I've seen before include "Perceive, watch" , "Three points" , "Bishop's area of control" , "Perceive with eyes or mind" , "Glimpse; get" .)