Prince at last with Cinders in best restaurant (3,4)
I believe the answer is:
tea shop
'restaurant' is the definition.
(tea shop is a kind of restaurant)
'prince at last with cinders in best' is the wordplay.
'at last' indicates one should take the final letters.
'with' says to put letters next to each other.
'cinders' becomes 'ash' (cinders can mean ashes).
'in' means one lot of letters goes inside another.
'best' becomes 'top' (top can mean the very best).
The last letter of 'prince' is 'e'.
'e'+'ash'='eash'
'eash' placed within 'top' is 'TEA-SHOP'.
(Other definitions for tea shop that I've seen before include "Cafe (paradoxically?)" , "Refreshments provider" , "refreshing facility" , "Small cafe" , "Restaurant serving light meals" .)