Fashionable greeting, quiet (3)
I believe the answer is:
hip
'fashionable' is the definition.
(hip can mean trendy or fashionable)
'greeting quiet' is the wordplay.
'greeting' becomes 'hi' (hi is a kind of greeting).
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'hi'+'p'='HIP'
(Other definitions for hip that I've seen before include "Trendy or stylish, like fruit of the wild rose" , "Fashionable" , "it can nowadays be replaced" , "flask here?" , "Slangily trendy part of body" .)