Tours' river (5)
I believe the answer is:
loire
'tours' river' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loire that I've seen before include "French department" , "valley famous for its wines" , "River flowing through Tours and Nantes" , "European river" , "French river (Orleans, Tours, Nantes)" .)