Works out limits of elegant plaything (5,3)
I believe the answer is:
train set
'plaything' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'works out limits of elegant' is the wordplay.
'works out' becomes 'trains' (training is a kind of working out).
'limits of' suggests removing the centre.
'elegant' with its centre taken out is 'et'.
'trains'+'et'='TRAIN-SET'
Can you help me to learn more?
(Other definitions for train set that I've seen before include "Toy railway" , "Number of tracked items" , "Model tracking" , "Nitrates (anag) - Hornby product?" , "A child might play with this" .)