Going back again to the same river (4)
I believe the answer is:
oder
'river' is the definition.
(Oder River is an example)
'going back again to the same' is the wordplay.
'going back' shows that the letters should be reversed in order.
'again' becomes 're'.
'to the same' becomes 'do'.
're'+'do'='redo'
'redo' written backwards gives 'ODER'.
(Other definitions for oder that I've seen before include "river, one in central Europe" , "River forming northern part of the German-Polish border" , "German and Polish river" , "School blazer insignia" , "flowing water" .)