Cannabis drug hidden in His Majesty's Prison (4)
I believe the answer is:
hemp
'cannabis' is the definition.
(I've seen this in another clue)
'drug hidden in his majesty's prison' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'hidden in' is an insertion indicator.
'his majesty' becomes 'hm' (short for His Majesty).
'prison' becomes 'p' (this could be a standard abbreviation which I don't know about).
'e' put within 'hm' is 'hem'.
'hem'+'p'='HEMP'
Can you help me to learn more?
(Other definitions for hemp that I've seen before include "Source of drug" , "Narcotic drug" , "Plant fibre used to make rope" , "Grass" , "Marijuana" .)