Casual hellos (3)
I believe the answer is:
his
'casual hellos' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for his that I've seen before include "Belonging to the male" , "Belonging to that man" , "It belongs to him" , "That man's" , "To - Coy Mistress (Marvell)" .)