It’s worn by drivers about to stop lady (7)
I believe the answer is:
macadam
'it's worn by drivers' is the definition.
(drivers wear down macadam on roads)
'to stop lady' is the wordplay.
'to' becomes 'ca' (I can't explain this - if you can you should believe this answer much more).
'stop' means one lot of letters goes inside another (stopping can mean blocking a gap).
'lady' becomes 'madam' (synonyms).
'ca' going into 'madam' is 'MACADAM'.
'about' acts as a link.
(Other definitions for macadam that I've seen before include "(Inventor of) road surface" , "Road surfacing material" , "Name associated with road surfaces" , "Road-surfacing material" , "Broken stones" .)