Dizziness (7)
I believe the answer is:
vertigo
'dizziness' is the definition.
(synonyms)
This is all the clue.
(Other definitions for vertigo that I've seen before include "Type of dizziness associated with fear of heights" , "Dizziness at height" , "Sensitivity to heights" , "unbalanced feeling" , "Forty Thieves' password" .)