Guard, pay attention to motorway area to the north (8)
I believe the answer is:
watchman
'guard' is the definition.
(watchman is a kind of guard)
'pay attention to motorway area to the north' is the wordplay.
'pay attention to' becomes 'watch'.
'motorway' becomes 'M' (as in motorway names - M1, M4 etc).
'area' becomes 'a' (maths abbreviation).
'to the north' becomes 'N' (abbreviation).
'watch'+'m'+'a'+'n'='WATCHMAN'
(Other definitions for watchman that I've seen before include "Security guard" , "fellow on duty?" , "Sentinel" , "Night guard" , "'Go Set a --', Harper Lee novel" .)