Road marker from motorway with large English letters (8)
I believe the answer is:
milepost
'road marker' is the definition.
(I've seen this in another clue)
'motorway with large english letters' is the wordplay.
'motorway' becomes 'MI' (resembles Mp, English motorway).
'with' is a charade indicator (letters next to each other).
'large' becomes 'L' (eg in clothes sizes).
'english' becomes 'E' (abbreviation).
'letters' becomes 'post' (letters in the mail or post).
'mi'+'l'+'e'+'post'='MILEPOST'
'from' acts as a link.
(Other definitions for milepost that I've seen before include "Eight-furlong marker" , "Distance marker" , "measure of progress" .)