Motorway beginning to generally limit movement (9)
I believe the answer is:
migration
'movement' is the definition.
(I have seen 'movement of people' mean 'migration' so perhaps 'movement' could also mean 'migration')
'motorway beginning to generally limit' is the wordplay.
'motorway' becomes 'MI' (resembles M1, English motorway).
'beginning to' says to take the initial letters.
'limit' becomes 'ration' (rationing is a kind of limiting).
The first letter of 'generally' is 'g'.
'mi'+'g'+'ration'='MIGRATION'
(Other definitions for migration that I've seen before include "Seasonal movement of animals or birds" , "The movement of people or animals from one locality to another" , "Roaming it? (anagram)" , "Periodic passage of animals from one place to another" , "Annual movement from one place to another" .)