Balance unsteadily (6)
I believe the answer is:
teeter
'balance unsteadily' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for teeter that I've seen before include "Totter, wobble" , "Rock unsteadily on edge" , "Sway back and forth on the edge" , "Sway, as if about to fall" , "Wobble on the brink" .)