Everything in the show is trivial (7)
I believe the answer is:
shallow
'trivial' is the definition.
(I've seen this before)
'everything in the show' is the wordplay.
'everything' becomes 'all' (all things).
'in the' is an insertion indicator.
'all' going inside 'show' is 'SHALLOW'.
'is' acts as a link.
(Other definitions for shallow that I've seen before include "12 [TWO DIMENSIONAL]" , "Of no great depth" , "Frivolous" , "Superficial" , "incapable of serious thought" .)