Drug controlled by Turkish Empire (4)

I believe the answer is:

hemp

I'm a little stuck... Click here to teach me more about this clue!

'drug' is the definition.
(I've seen this before)

'controlled by turkish empire' is the wordplay.
'HEMP' is hidden in amongst the letters.
But, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for hemp that I've seen before include "Source of drug" , "Plant fibre used to make rope" , "Narcotic drug" , "tea" , "Grass" .)

I've seen this clue in The Independent.

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