Teacher in coach overcoming motorway tension (14)
I believe the answer is:
schoolmistress
'teacher' is the definition.
(schoolmistress is a kind of teacher)
'coach overcoming motorway tension' is the wordplay.
'coach' becomes 'school' (I've seen this before).
'overcoming' says to put letters next to each other (some letters are written over others).
'motorway' becomes 'mi' (resembles Ms, English motorway).
'tension' becomes 'stress' ('stress' can be a synonym of 'tension'**).
'school'+'mi'+'stress'='SCHOOLMISTRESS'
'in' acts as a link.
(Another definition for schoolmistress that I've seen is " female teacher".)