Love at hotel to make promise (4)
I believe the answer is:
oath
'promise' is the definition.
(I know that oath is a type of promise)
'love at hotel' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'o'+'at'+'h'='OATH'
'to make' is the link.
(Other definitions for oath that I've seen before include "in court, we take it" , "Curse or solemn promise" , "Vow, sworn word" , "It's taken in court" , "Vow; profanity" .)