When crossing Roman road, note flies (7)
I believe the answer is:
aviates
'flies' is the definition.
('aviate' can be a synonym of 'fly')
'when crossing roman road note' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'crossing' means one lot of letters goes inside another (to cross can mean to go over or around).
'roman road' becomes 'via' (I've seen this before).
'note' becomes 'te' (musical note as in do re mi fa so la ti).
'via'+'te'='viate'
'as' placed around 'viate' is 'AVIATES'.
(Another definition for aviates that I've seen is " Flies".)