Observed a cutting tool (3)
I believe the answer is:
saw
I believe this clue is a double definition.
'observed' is the first definition.
(seen)
'a cutting tool' is the second definition.
(I've seen this before)
(Other definitions for saw that I've seen before include "Witnessed" , "Picked out" , "Carpenter's tool" , "Carpentry tool" , "The saying for cutting wood" .)