Notice a cutting tool go up and down
I believe the answer is:
seesaw
'go up and down' is the definition.
(I've seen this before)
'notice a cutting tool' is the wordplay.
'notice' becomes 'see' (notice can mean to spot or see).
'a cutting tool' becomes 'saw' (I've seen this before).
'see'+'saw'='SEESAW'
(Other definitions for seesaw that I've seen before include "Up-and-down motion" , "Board balanced on a fulcrum in the playground" , "'Move up and down alternately'" , "Up-and-down children's game with plank on barrel" , "Piece of playground equipment" .)