River that is cold before noon (3)
I believe the answer is:
cam
'river' is the definition.
(river in Cambridge, England)
'cold before noon' is the wordplay.
'cold' becomes 'C' (eg on taps).
'before noon' becomes 'AM' (as in AM on a clock).
'c'+'am'='CAM'
'that is' is the link.
(Other definitions for cam that I've seen before include "East Anglian river" , "Rotating projection; river" , "Tributary of the Ouse" , "Projection on rotating shaft imparting motion" , "Bump on a shaft for pushing another shaft" .)