River possibly making a U-bend (6)
I believe the answer is:
danube
'river' is the definition.
(I know that Danube is a river)
'making a u-bend' is the wordplay.
'making' indicates anagramming the letters.
'a'+'u'+'bend'='aubend'
'aubend' with letters rearranged gives 'DANUBE'.
'possibly' is the link.
(Other definitions for danube that I've seen before include "Ban due (anag) - river" , "5 down's river" , "River flowing from Black Forest to Black Sea" , "Vienna's river" , "River flowing through Belgrade, Budapest and Vienna" .)