Victor joins Olga on the river (5)
I believe the answer is:
Here is my best explanation:
'the river' is the definition.
(Volga is an example)
'victor joins olga' is the wordplay.
'victor' becomes 'v' (phonetic alphabet: alpha, bravo, charlie etc.).
'joins' means one lot of letters go next to another.
'on' acts as a link.