Scottish engineer, vulgar sort, interrupting formal greeting to woman (7)
I believe the answer is:
macadam
'formal greeting to woman' is the definition.
I can't judge whether this defines the answer.
'scottish engineer vulgar sort interrupting' is the wordplay.
'scottish engineer' becomes 'McAdam' (a8th- and a9th-century engineer John Loudon McAdam).
'vulgar sort' becomes 'a' (I can't justify this - if you can you should believe this answer much more).
'interrupting' is an insertion indicator.
'mcadam' going around 'a' is 'MACADAM'.
Can you help me to learn more?
(Other definitions for macadam that I've seen before include "Road-surfacing material" , "Material for roads" , "Broken stones" , "stones on the way" , "Road surface made of broken stone and tar" .)