Military prison is unsuitable place for stoner? (10)

I believe the answer is:

glasshouse

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

'military prison' is the definition.
'glasshouse' can be an answer for 'prison' (I've seen this before). I'm not sure about the 'military' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for glasshouse that I've seen before include "Military detention centre (informal)" , "Building for plants; prison" , "where no one should be stoned?" , "Conservatory - military detention centre" , "where lapidation is not recommended?" .)

I've seen this clue in The Times.

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