In a glass case, so to speak (7)
I believe the answer is:
bottled
'in' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs can sometimes mean the same thing.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for bottled that I've seen before include "confined by Nebuchadnezzar?" , "Attacked in pub" , "Preserved in jars" , "Stored in glass" .)