Concerns a child’s motivations (7)

I believe the answer is:

reasons

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'motivations' is the definition.
(I know this)

'concerns a child's' is the wordplay.
'concerns' becomes 'rea' (I can't explain this - if you can you should believe this answer much more).
'a child's' becomes 'sons' (male child).
'rea'+'sons'='REASONS'

Can you help me to learn more?

(Other definitions for reasons that I've seen before include "Logically deduces" , "Debates; thinks out" , "Period of reduced economic activity" , "Infers logically" , "excuses" .)

I've seen this clue in the Sydney Morning Herald.

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