The way on from Rouen (3)
I believe the answer is:
'the way' is the definition.
(I have seen 'French way' mean 'rue' so perhaps 'way' could also mean 'rue')
'on from rouen' is the wordplay.
'from' indicates named letters should be taken away.
'rouen' with 'on' taken out is 'RUE'.
(Other definitions for rue that I've seen before include "Regret the bitter herb", "Deplore", "Bitterly regret - plant", "At one time, pity", "Nice way".)