The man's greetings (3)
I believe the answer is:
his
This clue is a double definition.
'the man's' is the first definition.
(thesaurus)
'greetings' is the second definition.
(hi is a kind of greeting)
(Other definitions for his that I've seen before include "That man's" , "Belonging to that man" , "To - Coy Mistress (Marvell)" , "that chap's" , "It belongs to him" .)