Everything in the show is superficial (7)
'superficial' is the definition.
(similar in meaning)
'everything in the show' is the wordplay.
'everything' becomes 'all' (all things).
'in the' indicates putting letters inside.
'all' placed inside 'show' is 'SHALLOW'.
'is' is the link.
(Other definitions for shallow that I've seen before include "Not profound" , "12 [TWO DIMENSIONAL]" , "Insincere" , "flimsy" , "Having little depth" .)
'everything' is the definition.
(all things)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for all that I've seen before include "The whole quantity" , "that's as many as there are" , "The lot, everyone" , "The whole amount" , "Quite" .)