Official also must drop in (3)

I believe the answer is:

aga

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'official' is the definition.
(I have seen 'Military official' mean 'aga' so perhaps 'official' could also mean 'aga')

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for aga that I've seen before include "Military commander in the Ottoman Empire" , "Oven" , "--- Khan, spiritual head of Ismaili Muslims" , "of the 17 [KITCHEN]" , "Chief officer" .)

I've seen this clue in The Times.

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