Observe present and past plaything (6)
I believe the answer is:
seesaw
I believe this is a double definition.
'observe present and past' is the first definition.
(see present tense and saw past tense)
'plaything' is the second definition.
(seesaw is a kind of plaything)
(Other definitions for seesaw that I've seen before include "entertainment for children" , "It goes up and down with the child" , "Recreation ground item" , "yo-yo" , "Children's plaything with plank over barrel" .)