Storage space of quiet mischievous being (5)
I believe the answer is:
shelf
'storage space' is the definition.
(I've seen this in another clue)
'quiet mischievous being' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'mischievous being' becomes 'elf' (I've seen this in another clue).
'sh'+'elf'='SHELF'
'of' acts as a link.
(Other definitions for shelf that I've seen before include "Ledge for books etc" , "Works are held up by it" , "Sill" , "Horizontal surface for holding objects" , "grass down under" .)