Large furniture store's fashionable instantly (4,1,4)
I believe the answer is:
like a shot
'instantly' is the definition.
(I've seen this before)
'large furniture store's fashionable' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'furniture store's' becomes 'IKEA's' (Swedish furniture company).
'fashionable' becomes 'hot' (hot can mean fashionable or trendy).
'l'+'ikeas'+'hot'='LIKE A SHOT'
(Other definitions for like a shot that I've seen before include "Enjoy a nip" , "At once, willingly" , "Outright" , "Fancy a drop to drink" , "Lout" .)