Marched in a line, crossing motorway, and shot (6)
I believe the answer is:
filmed
'shot' is the definition.
('film' can be a synonym of 'shoot')
'marched in a line crossing motorway' is the wordplay.
'marched in a line' becomes 'filed' (to file is to walk or march in a line or file).
'crossing' indicates putting letters inside.
'motorway' becomes 'm'.
'filed' placed around 'm' is 'FILMED'.
'and' acts as a link.
(Other definitions for filmed that I've seen before include "Made a movie" , "Made for cinema" , "Shot" .)