Not liking river, boy rising on opposite side (9)
I believe the answer is:
antipodal
'on opposite side' is the definition.
'not liking river boy rising' is the wordplay.
'not liking' becomes 'anti'.
'river' becomes 'po' (Po is an example).
'boy' becomes 'lad' (lad is a kind of boy).
'rising' is a reversal indicator (going up in a down clue).
'lad' backwards is 'dal'.
'anti'+'po'+'dal'='ANTIPODAL'
(Other definitions for antipodal that I've seen before include "in NZ, say" , "Opposite" .)