Host penning song, greeting Latin musician (8)
I believe the answer is:
mariachi
'latin musician' is the definition.
(as in a mariachi band)
'host penning song greeting' is the wordplay.
'host' becomes 'mc' (short for master of ceremonies).
'penning' means one lot of letters goes inside another.
'song' becomes 'aria' (aria is a kind of song).
'greeting' becomes 'hi' (hi is a kind of greeting).
'mc' going around 'aria' is 'mariac'.
'mariac'+'hi'='MARIACHI'
(Other definitions for mariachi that I've seen before include "Source of Mexican music" , "one who performs music" , "Traditional Mexican folk music" , "Mexican street musician" , "Utters" .)