Stagger back getting unbalanced (4)
I believe the answer is:
nuts
'unbalanced' is the definition.
(I've seen this before)
'stagger back' is the wordplay.
'stagger' becomes 'stun' (I've seen this before).
'back' says the letters should be written in reverse.
'stun' reversed gives 'NUTS'.
'getting' is the link.
(Other definitions for nuts that I've seen before include "Barmy (colloq)" , "deprived of one's wits" , "Fruit with edible kernel" , "Hard-shelled fruits or seeds" , "Heads - fans - fruit" .)