Everything in the show is superficial (7)
I believe the answer is:
shallow
'is superficial' is the definition.
(similar in meaning)
'everything in the show' is the wordplay.
'everything' becomes 'all' (all things).
'in the' means one lot of letters goes inside another.
'all' inserted within 'show' is 'SHALLOW'.
(Other definitions for shallow that I've seen before include "Not profound" , "12 [TWO DIMENSIONAL]" , "Insincere" , "flimsy" , "Having little depth" .)