Playthings for unbalanced children (7)
I believe the answer is:
seesaws
'playthings' is the definition.
(seesaw is a kind of plaything)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for seesaws that I've seen before include "Yo-yos" , "Playthings in the park" , "Playground games" , "Pieces of playground furniture" , "Boards balanced on fulcrums, children's playthings" .)