Work on wall shows Frenchman going over Russian river (5)
I believe the answer is:
mural
'work on wall' is the definition.
'frenchman going over russian river' is the wordplay.
'frenchman' becomes 'm' (abbreviation for Monsieur - like 'Mr').
'going over' says to put letters next to each other.
'russian river' becomes 'ural' (I've seen this in other clues).
'm'+'ural'='MURAL'
'shows' acts as a link.
(Other definitions for mural that I've seen before include "Painting on a wall, fresco" , "Artwork" , "Drawing on a wall" , "Wall-painting" , "Large wall painting" .)