Crossword Genius

The main part of the earth (5)

Ross

I believe the answer is:

ocean

I believe this clue is a double definition.

'the main' is the first definition.
('ocean' can be a synonym of 'main')

'part of the earth' is the second definition.
('ocean' is part of 'earth')

(Other definitions for ocean that I've seen before include "An immense expanse of sea" , "Quantity of water" , "Sea - canoe (anag)" , "Vast sea" , "Big sea" .)

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