School arranged something for kids' amusement (5,3)
I believe the answer is:
train set
'something for kids' amusement' is the definition.
'school arranged' is the wordplay.
'school' becomes 'train' (training is a kind of schooling).
'arranged' becomes 'set' (similar in meaning).
'train'+'set'='TRAIN SET'
(Other definitions for train set that I've seen before include "Layout with engines" , "Toy with rail track" , "Nitrates (anag) - Hornby product?" , "Model tracking" , "A child might play with this" .)