O, VP! (6,2,7)

I believe the answer is:

second in command

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'o' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for second in command that I've seen before include "deputy leader" , "He's close to the boss" , "number two" , "given only the most short-lived responsibility!" , "Officer" .)

I've seen this clue in The Independent.

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