See river terrace (6)
I believe the answer is:
exeter
'see' is the definition.
(I've seen this before)
'river terrace' is the wordplay.
'river' becomes 'exe' (River Exe).
'terrace' becomes 'ter' (I've seen this in other clues).
'exe'+'ter'='EXETER'
(Other definitions for exeter that I've seen before include "English university city" , "English cathedral city" , "See" , "County town and cathedral city of Devon" , "Administrative centre of Devon" .)