Regularly dropping oars, I annoy cox endlessly leading us to river (7)

I believe the answer is:

orinoco

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'river' is the definition.
(Orinoco River is an example)

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

(Other definitions for orinoco that I've seen before include "River, rising in Venezuela, forming part of its border with Colombia and flowing into the Atlantic" , "Great river in the north of S America, flows through Venezuela" , "Womble; S. Amer. river" , "South-American river" , "South American river flowing into the Atlantic" .)

I've seen this clue in The Everyman puzzle in The Observer.

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