Enter into an arrangement for storage (9)
I believe the answer is:
retention
'storage' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'enter into an arrangement' is the wordplay.
'an arrangement' indicates an anagram.
'enter'+'into'='enterinto'
'enterinto' with letters rearranged gives 'RETENTION'.
'for' is the link.
Can you help me to learn more?
(Other definitions for retention that I've seen before include "Capacity to remember" , "Keeping hold (of something)" , "memory" , "Enter into custody" , "maintenance" .)