Seller of rare tile design (8)
I believe the answer is:
retailer
'seller' is the definition.
(I know that retailer is a type of seller)
'rare tile design' is the wordplay.
'design' indicates an anagram.
'rare'+'tile'='raretile'
'raretile' with letters rearranged gives 'RETAILER'.
'of' acts as a link.
(Other definitions for retailer that I've seen before include "teller" , "One selling to public" , "Store-keeper" , "High street trader?" , "Merchant" .)