Man blocks view in main route (3,4)

I believe the answer is:

sea lane

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

'main route' is the definition.
'sea lane' can be an answer for 'route' (thesaurus). I am unsure of the 'main' bit.

'man blocks view' is the wordplay.
'man' becomes 'alan' ().
'blocks' is an insertion indicator (the inside letters form a 'blockage').
'view' becomes 'see' (synonyms).
'alan' put within 'see' is 'SEA LANE'.

'in' is the link.

Can you help me to learn more?

(Another definition for sea lane that I've seen is " marine passage".)

I've seen this clue in The Independent and The Sun.

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