Sound of lots of people in store (5)
I believe the answer is:
hoard
'store' is the definition.
(I know this)
'sound of lots of people' is the wordplay.
'sound of' shows a homophone (sound like).
'lots of people' becomes 'horde' (I've seen this in another clue).
'horde' sounds like 'HOARD'.
'in' is the link.
(Other definitions for hoard that I've seen before include "Secret store of valuables" , "Stockpile" , "Cache" , "Collection" , "Store of money or valuables" .)