Leaving storage that's not bespoke (3,3,5)
I believe the answer is:
off the shelf
'not bespoke' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs occasionally mean the same thing.
'leaving storage' is the wordplay.
'leaving' becomes 'off' (as in 'I'm off').
'storage' becomes 'theshelf' (I can't explain this - if you can you should believe this answer much more).
'off'+'theshelf'='OFF-THE-SHELF'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for off the shelf that I've seen before include "Not specially prepared" , "What old maid isn't" , "immediately available" , "to be married at last?" , "description of instant bestseller?" .)