Notice North America exploit a motorway tediously (2,7)
I believe the answer is:
ad nauseam
'tediously' is the definition.
Both the answer and definition are adverbs. Maybe there's an association between them I don't understand?
'notice north america exploit a motorway' is the wordplay.
'notice' becomes 'ad' (short for advert).
'north america' becomes 'na'.
'exploit' becomes 'use' (use can mean to exploit).
'motorway' becomes 'M' (as in motorway names - M1, M4 etc).
'ad'+'na'+'use'+'a'+'m'='AD NAUSEAM'
Can you help me to learn more?
(Other definitions for ad nauseam that I've seen before include "To a disgusting extent" , "Done so often that it becomes tiresome" , "On and on - would make you sick" , "Past the stage of enjoying" , "Much too much" .)