To applaud role coming up is nonsense (8)
I believe the answer is:
claptrap
'is nonsense' is the definition.
(thesaurus)
'to applaud role coming up' is the wordplay.
'to applaud' becomes 'clap' ('clap' can be a synonym of 'applaud').
'role' becomes 'part' ('part' can be a synonym of 'role').
'coming up' says the letters should be written backwards.
'part' back-to-front is 'trap'.
'clap'+'trap'='CLAPTRAP'
(Other definitions for claptrap that I've seen before include "Pretentious talk used to win applause" , "Bunk" , "Meaningless, insincere or pompous talk" , "Bull" , "Tripe" .)