Silly relation taken in by hollow invective (5)
I believe the answer is:
inane
'silly' is the definition.
(thesaurus)
'relation taken in by hollow invective' is the wordplay.
'relation' becomes 'nan' (I've seen this before).
'taken in by' is an insertion indicator.
'hollow' says to hollow out the word (remove centre letters).
'invective' with its middle taken out is 'ie'.
'nan' going inside 'ie' is 'INANE'.
(Other definitions for inane that I've seen before include "Without meaning or point" , "unimaginative" , "Empty" , "Idiotic" , "Really stupid" .)