Happiness of one in top hotel (7)
I believe the answer is:
triumph
'happiness' is the definition.
(I know that triumph is a type of exultation)
'one in top hotel' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'top' becomes 'trump' (both can mean to beat or outdo).
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'i' inserted within 'trump' is 'triump'.
'triump'+'h'='TRIUMPH'
'of' is the link.
(Other definitions for triumph that I've seen before include "Exultant victory" , "Exult in victory" , "Crow" , "hit" , "beat the opposition!" .)