Storage units do not include quiet pixies (5)
I believe the answer is:
elves
'pixies' is the definition.
('elf' can be a synonym of 'pixy')
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for elves that I've seen before include "Legendary little beings" , "mischievous kids?" , "Troublemakers" , "Santa's little helpers" , "Capricious folk" .)