Note article by small auction house (8)
I believe the answer is:
sothebys
'auction house' is the definition.
(Sotheby's is an auction house)
'note article by small' is the wordplay.
'note' becomes 'so' (musical note).
'article' becomes 'the' (the definite article in English).
'small' becomes 's' (abbreviation - e.g. clothes size).
'so'+'the'+'by'+'s'='SOTHEBYS'
(Other definitions for sothebys that I've seen before include "Famous auction house" , "Auctioneers" .)