Commanding officers with a chocolate drink (5)

I believe the answer is:

cocoa

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

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

Can you help me to learn more?

(Other definitions for cocoa that I've seen before include "Nighttime drink" , "Hot bedtime drink" , "Medium to dark brown" , "Powder from cacao beans" , "Chocolate ingredient" .)

I've seen this clue in The Daily Express.

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