Seller with Visa unusual in palace location (10)
I believe the answer is:
versailles
'palace location' is the definition.
The definition suggests a singular noun which matches the answer.
'seller with visa unusual' is the wordplay.
'with' says to put letters next to each other.
'unusual' indicates an anagram.
'seller' put after 'visa' is 'visaseller'.
'visaseller' anagrammed gives 'VERSAILLES'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for versailles that I've seen before include "Royal Court" , "Louis XIV's palace; WW one treaty" , "French palace" , "Palace built by Louis XIV" , "Palace near Paris" .)