Your Highness? (8)
I believe the answer is:
altitude
'highness?' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for altitude that I've seen before include "Height (above ground)" , "Height, elevation" , "high place" , "Lofty position" , "Loftiness" .)