End of a motorway going west (3)
I believe the answer is:
aim
'end' is the definition.
(both can mean a purpose or goal)
'a motorway going west' is the wordplay.
'motorway' becomes 'MI' (resembles M1, English motorway).
'going west' is a reversal indicator (letters heading to the west or left).
'mi' reversed gives 'im'.
'a'+'im'='AIM'
'of' acts as a link.
(Other definitions for aim that I've seen before include "mission" , "Purpose in directing the rifle" , "This is mean" , "Ambition or goal" , "Point (a camera)" .)