The man who prepares the main dishes? (3-4)

I believe the answer is:

sea-cook

I'm a little stuck... Click here to teach me more about this clue!

'the man who prepares' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'main dishes?' is the wordplay.
'main' becomes 'sea' (the main is an old name for the sea).
'dishes?' becomes 'cook' (I can't explain this - if you can you should believe this answer much more).
'sea'+'cook'='SEA-COOK'

'the' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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