Clyde, say (5)
I believe the answer is:
river
'clyde say' is the definition.
(I know that Clyde is a river)
This is all the clue.
(Other definitions for river that I've seen before include "Eg, the Rhine" , "course of 1d [ADVENTURE]" , "x or y, so to speak" , "Type of watercourse" , "flower" .)