Right in the main? (9)

I believe the answer is:

starboard

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'right' is the definition.
(right side of a ship)

I cannot understand how the rest of the clue works.

(Other definitions for starboard that I've seen before include "One side of a ship" , "Right side of ship or plane" , "Sailor's right" , "Literally, the steering side of a vessel" , "Right-hand side of ship while facing forward" .)

I've seen this clue in The Telegraph.

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