Talk about new slogan (5)
I believe the answer is:
chant
'slogan' is the definition.
'talk about new' is the wordplay.
'talk' becomes 'chat' (chat can mean to talk).
'about' is an insertion indicator.
'new' becomes 'n' (abbreviation as in New Testament NT).
'chat' placed around 'n' is 'CHANT'.
(Other definitions for chant that I've seen before include "Mantra" , "Repeated rhythmic song" , "Incantatory song" , "Type of group singing" , "Recite singingly" .)