Put off by people on motorway showing single-mindedness (13)
I believe the answer is:
determination
'single-mindedness' is the definition.
(thesaurus)
'put off by people on motorway' is the wordplay.
'put off' becomes 'deter' (I've seen this before).
'by' says to put letters next to each other.
'people' becomes 'nation' (**).
'on' means one lot of letters go next to another.
'motorway' becomes 'mi' (resembles Mn, English motorway).
'nation' put after 'mi' is 'mination'.
'deter' next to 'mination' is 'DETERMINATION'.
'showing' acts as a link.
(Other definitions for determination that I've seen before include "Firm resolve" , "Willpower" , "24 [DRIVE]" , "Resoluteness" , "Decision process" .)