Be quiet fairy on ledge (5)
I believe the answer is:
shelf
'ledge' is the definition.
(I know that ledge can be written as shelf)
'be quiet fairy on' is the wordplay.
'be quiet' becomes 'sh' (both are said to tell someone to stop speaking).
'fairy' becomes 'elf' (elf is a kind of fairy).
'on' says to put letters next to each other.
'sh'+'elf'='SHELF'
(Other definitions for shelf that I've seen before include "Rock ledge; underwater bank" , "Storage ledge" , "Ledge for books etc" , "Flat rectangular structure in house for putting things on" , "Sill" .)