Coat turning up in river (3)
I believe the answer is:
cam
'river' is the definition.
(river in Cambridge, England)
'coat turning up' is the wordplay.
'coat' becomes 'mac' (mac is a kind of coat).
'turning up' says the letters should be written in reverse.
'mac' back-to-front is 'CAM'.
'in' is the link.
(Other definitions for cam that I've seen before include "English river" , "Rotating mechanism" , "running through university city?" , "River also called Granta" , "Part of engine" .)