Resolve to put off motorway race (13)
I believe the answer is:
determination
'resolve' is the definition.
(determination is a kind of resolve)
'put off motorway race' is the wordplay.
'put off' becomes 'deter' (I've seen this before).
'motorway' becomes 'mi' (resembles M1, English motorway).
'race' becomes 'nation' (I've seen this before).
'deter'+'mi'+'nation'='DETERMINATION'
'to' is the link.
(Other definitions for determination that I've seen before include "Willpower" , "Resolution" , "Resoluteness" , "legal decision" , "Perseverance" .)