Moves back and forth or from side to side while suspended (6)
I believe the answer is:
swings
'moves back and forth or from side to side while suspended' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for swings that I've seen before include "What you lose on these, you'll gain on the roundabouts" , "Sways" , "Moves back and forth or from side to side while suspended" , "Moves to and fro like pendulum" , "What you might lose on them, you could gain on the roundabouts" .)