Lost one's balance? (5)
I believe the answer is:
spent
'lost one's balance?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for spent that I've seen before include "Worn out having paid out money." , "Used up; exhausted" , "Exhausted, having paid money?" , "Worn out - after shopping?" , "Paid out - finished" .)