Sea child's most important problem? (4,5)

I believe the answer is:

main issue

'most important problem?' is the definition.
(the most pressing issue or problem)

'sea child's' is the wordplay.
'sea' becomes 'main' (synonyms).
'child' becomes 'issue' (I've seen this before).
'main'+'issue'='MAIN ISSUE'

I've seen this clue in The Guardian.

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