He will ring in greeting (5)
I believe the answer is:
hello
'greeting' is the definition.
(hello is a kind of greeting)
'he will ring' is the wordplay.
'will' becomes 'll'.
'ring' becomes 'o'.
'he'+'ll'+'o'='HELLO'
'in' is the link.
(Other definitions for hello that I've seen before include "A salutation" , "I say" , "Conversation starter" , "Introductory greeting" , "Musical with Satchmo and Streisand" .)