Selection of music at school show (4)
I believe the answer is:
cats
'show' is the definition.
(I've seen this before)
'selection of music at school' is the wordplay.
'selection of' indicates a hidden word.
'CATS' can be found hidden inside 'music at school'.
(Other definitions for cats that I've seen before include "Musical; jazz fans" , "Spectacular Llyod Webber feline musical" , "Siamese, Persian etc" , "Popular musical" , "Musical (felines?)" .)