Notwithstanding, tips back into the river (7)
I believe the answer is:
despite
'notwithstanding' is the definition.
(thesaurus)
'tips back into the river' is the wordplay.
'back' shows that the letters should be reversed in order.
'into' is an insertion indicator.
'the river' becomes 'dee' (River Dee).
'tips' back-to-front is 'spit'.
'spit' inserted inside 'dee' is 'DESPITE'.
(Other definitions for despite that I've seen before include "Notwithstanding" , "Undeterred" , "Without being affected by; contempt" , "In the face" , "Regardless of, in defiance of" .)