Crowd in store, by the sound of it (5)
I believe the answer is:
horde
'crowd' is the definition.
(horde is a kind of crowd)
'store by the sound of it' is the wordplay.
'store' becomes 'hoard' (hoarding is a kind of storing).
'by the sound of it' shows a homophone (sound like).
'hoard' is a homophone of 'HORDE'.
'in' is the link.
(Other definitions for horde that I've seen before include "Vast crowd" , "Huge noisy crowd" , "Throng, mass" , "Nomadic army" , "lots of people" .)