Gone off to river, pursuing affectionate hawk (9)
I believe the answer is:
warmonger
'hawk' is the definition.
(hawk can mean someone urging military action)
'gone off to river pursuing affectionate' is the wordplay.
'off' indicates an anagram.
'to river' becomes 'r' (abbreviation).
'pursuing' is a charade indicator (letters next to each other).
'affectionate' becomes 'warm' (synonyms).
'gone' with letters rearranged gives 'onge'.
'onge'+'r'='onger'
'onger' after 'warm' is 'WARMONGER'.
(Other definitions for warmonger that I've seen before include "Hawk" , "Belligerent person" , "Aggressor" , "Bellicose type" , "Jingoistic individual" .)