Hotel number for your highness? (6)
I believe the answer is:
height
'your highness?' is the definition.
(how tall or 'high' you are)
'hotel number' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'number' becomes 'eight' (eight is a kind of number).
'h'+'eight'='HEIGHT'
'for' acts as a link.
(Other definitions for height that I've seen before include "Measurement from base to top" , "Rising ground; extreme example" , "Vertical dimension" , "Measure it from top to bottom" , "part of a patient's statistics?" .)