Whirling sensation when balance is disturbed (7)
I believe the answer is:
vertigo
'whirling sensation when balance is disturbed' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for vertigo that I've seen before include "Lightheadedness, dizziness" , "that makes it hard to stand" , "Dizzy sensation brought on by heights" , "Dizziness due to disorder in sense of balance" , "source of imbalance" .)