Bonnie's partner seen in river (5)
I believe the answer is:
clyde
I believe this is a double definition.
'bonnie's partner' is the first definition.
(crime duo Bonnie and Clyde)
'river' is the second definition.
(I know that Clyde is a river)
'seen in' acts as a link.
(Other definitions for clyde that I've seen before include "bank robber" , "Bonnie's partner" , "River of western Scotland" , "Flower of Scotland" , "Criminal" .)