Try to include finale that's fashionable (6)
I believe the answer is:
trendy
'fashionable' is the definition.
(similar in meaning)
'try to include finale' is the wordplay.
'to include' is an insertion indicator.
'finale' becomes 'end' (the end of a story or show).
'try' placed around 'end' is 'TRENDY'.
'that's' is the link.
(Other definitions for trendy that I've seen before include "following fashion" , "Informally fashionable" , "Stylish" , "Up to date, fashionable" , "Fashionable, in style" .)