Gridlock on motorway going west — go east (7)
I believe the answer is:
impasse
'gridlock' is the definition.
(I've seen this before)
'motorway going west go east' is the wordplay.
'motorway' becomes 'mi' (resembles Mp, English motorway).
'going west' shows that the letters should be reversed in order.
'go' becomes 'pass' (synonyms).
'east' becomes 'e' (synonyms).
'mi' backwards is 'im'.
'im'+'pass'+'e'='IMPASSE'
'on' acts as a link.
(Other definitions for impasse that I've seen before include "Standstill" , "failure to progress" , "There's no way past it" , "Situation of deadlock" , "hopeless difficulty" .)