Source of drugs, I note, given to male politician (6,4)

I believe the answer is:

indian hemp

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'source of drugs' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'i note given to male politician' is the wordplay.
'i' becomes 'india' (India is I in the NATO phonetic alphabet).
'note given' becomes 'n' (abbreviation. I am not sure about the 'given' bit.).
'to male' becomes 'he' (he refers to a man).
'politician' becomes 'MP' (Member of Parliament).
'india'+'n'+'he'+'mp'='INDIAN HEMP'

Can you help me to learn more?

(Other definitions for indian hemp that I've seen before include "familiar to ropemaker?" , "Pot plant" , "cannabis supplier" , "used as source of drugs" .)

I've seen this clue in The Guardian.

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