Observe a tool used by children
I believe the answer is:
seesaw
'observe a tool used by children' is the definition.
I can't tell whether this definition defines the answer.
'observe a tool used by' is the wordplay.
'observe' becomes 'see' (I've seen this before).
'a tool' becomes 'saw' (saw is a kind of tool).
'used by' means one lot of letters go next to another.
'see'+'saw'='SEESAW'
Can you help me to learn more?
(Other definitions for seesaw that I've seen before include "Plaything that's ridden up and down" , "having to move from one extreme to the other" , "Move back and forth" , "Playground equipment for kids" , "Oscillate" .)