In need of a lift, in the main?

I believe the answer is:

at sea

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'in the main?' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for at sea that I've seen before include "all over the place?" , "Totally disorganised" , "Muddled on the ocean?" , "'Filled with bewilderment (2,3)'" , "In confusion" .)

I've seen this clue in The Telegraph.

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