Piece of playground equipment (6)
I believe the answer is:
seesaw
'piece of playground equipment' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for seesaw that I've seen before include "Rise and fall" , "Vacillate; playground feature" , "Up-and-down children's game with plank on barrel" , "source of imbalance" , "'Move up and down alternately'" .)