Gold and diamonds outside empty shop a promising sign (7)
I believe the answer is:
auspice
'a promising sign' is the definition.
'auspice' can be an answer for 'sign' (auspice is a kind of sign). I'm not sure about the 'a promising' bit.
'gold and diamonds outside empty shop' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'and' means one lot of letters go next to another.
'diamonds' becomes 'ice' (slang term for diamonds).
'outside' is an insertion indicator (some letters go outside others).
'empty' suggests removing the centre.
'shop' with its centre removed is 'sp'.
'au'+'ice'='auice'
'auice' going around 'sp' is 'AUSPICE'.
Can you help me to learn more?
(Other definitions for auspice that I've seen before include "Omen - I use cap (anag)" , "Portent" , "future promise" , "Omen; epic USA (anag.)" , "Sign" .)