Stubborn fellow deceived about river vessel (9)
I believe the answer is:
hardliner
'stubborn fellow deceived' is the definition.
I can't judge whether this definition defines the answer.
'about river vessel' is the wordplay.
'about river' becomes 'hard' (I am not sure about this - if you are sure you should believe this answer much more).
'vessel' becomes 'liner' (liner is a kind of vessel).
'hard'+'liner'='HARDLINER'
Can you help me to learn more?
(Other definitions for hardliner that I've seen before include "dogmatic type" , "Doctrinaire type" , "Resolute advocate" , "One pursuing an uncompromising policy" , "Uncompromising advocate" .)