Applaud a catch? Nonsense (8)
I believe the answer is:
claptrap
'nonsense' is the definition.
(informal term meaning nonsense or rubbish)
'applaud a catch?' is the wordplay.
'applaud' becomes 'clap' (synonyms).
'a catch?' becomes 'trap' (I've seen this before).
'clap'+'trap'='CLAPTRAP'
(Other definitions for claptrap that I've seen before include "Cobblers" , "Pretentious talk used to win applause" , "Utter rubbish" , "Meaningless nonsense" , "Absurd or nonsensical talk or ideas" .)