Friend, in a major way (3)
I believe the answer is:
ami
'friend' is the definition.
('friend' in French)
'a major way' is the wordplay.
'major way' becomes 'mi' (resembles M1, English motorway).
'a'+'mi'='AMI'
'in' is the link.
(Other definitions for ami that I've seen before include "Parisian's friend" , "friend abroad?" , "A male friend in France" , "buddy" , "Mon . . . - my French friend" .)