Applaud retiring constituent? Rubbish! (8)
I believe the answer is:
claptrap
'rubbish' is the definition.
(thesaurus)
'applaud retiring constituent?' is the wordplay.
'applaud' becomes 'clap' ('clap' can be a synonym of 'applaud').
'retiring' shows that the letters should be reversed in order.
'constituent?' becomes 'part' (constituent is a kind of part).
'part' reversed gives 'trap'.
'clap'+'trap'='CLAPTRAP'
(Other definitions for claptrap that I've seen before include "Foolish or pretentious talk" , "Bunk" , "Stuff and nonsense" , "Pretentious talk or nonsense" , "High-sounding nonsense" .)