Surprisingly heightens saddle, getting vertigo (5-10)
I believe the answer is:
light-headedness
'vertigo' is the definition.
(I know that light-headedness is a type of vertigo)
'surprisingly heightens saddle getting' is the wordplay.
'surprisingly' indicates anagramming the letters (a surprising ordering of the letters).
'getting' is a charade indicator (letters next to each other).
'heightens'+'saddle'='heightenssaddle'
'heightenssaddle' with letters rearranged gives 'LIGHT-HEADEDNESS'.
(Another definition for light-headedness that I've seen is " Drunk feeling".)