How kids at the playground become accustomed to a new routine? (3,4,3,5)

'routine?' is the definition.
Both the answer and definition are adjectives.
Perhaps they are linked in a way I don't understand?

'how kids at the playground become accustomed to a new' is the wordplay.
I cannot quite see how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'become' could be 'get' (synonyms) and 'get' is located in the answer.
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?