Somerset city (5)
I believe the answer is:
wells
'somerset city' is the definition.
(Wells is a city in Somerset)
This is the entire clue.
(Other definitions for wells that I've seen before include "H. G. . . . . ., science-fiction writer" , "Springs" , "Cathedral city; sci-fi writer" , "Flows upward; small city" , "What a boring person might produce" .)