Waiting in a large shop (2,5)
I believe the answer is:
in store
'waiting' is the definition.
(I've seen this before)
'in a large shop' is the wordplay.
'a large shop' becomes 'store' (I've seen this before).
'in'+'store'='IN-STORE'
(Other definitions for in store that I've seen before include "Awaiting delivery" , "coming soon" , "stocked" , "Soon to happen" , "Waiting" .)