Argument about club in river (6)
I believe the answer is:
debate
'argument' is the definition.
(I know that argument can be written as debate)
'club in river' is the wordplay.
'club' becomes 'bat' (as in sporting equipment).
'in' means one lot of letters goes inside another.
'river' becomes 'dee' (River Dee).
'bat' put inside 'dee' is 'DEBATE'.
'about' acts as a link.
(Other definitions for debate that I've seen before include "Ponder" , "Discussion with arguments for and against" , "Discuss; argue" , "Public discussion, perhaps a contest" , "Discuss (in parliament)" .)