Kept in a glass case, so to speak! (7,2)

I believe the answer is:

bottled up

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

'kept' is the definition.
(bottling up is a kind of keeping)

I can't explain the rest of the clue.

(Another definition for bottled up that I've seen is " Kept back".)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app