Sister loves visiting city in Oregon — lots to see there? (9)
I believe the answer is:
salesroom
'lots to see there?' is the definition.
(where lots in an auction might be viewed)
'sister loves visiting city in oregon' is the wordplay.
'sister' becomes 'sr' (abbreviation as in names of nuns).
'loves' becomes 'oo' (love means 0 in tennis).
'visiting' is an insertion indicator.
'city in oregon' becomes 'Salem' (capital of Oregon).
'sr'+'oo'='sroo'
'sroo' inserted within 'salem' is 'SALESROOM'.
(Other definitions for salesroom that I've seen before include "marketing area" , "Where items for sale are displayed" , "Part of shop" , "Shop display area" .)