Drunk crosses motorway verge (5)
I believe the answer is:
limit
'verge' is the definition.
(I've seen this before)
'drunk crosses motorway' is the wordplay.
'drunk' becomes 'lit' (I've seen this in another clue).
'crosses' means one lot of letters goes inside another.
'motorway' becomes 'MI' (resembles Ml, English motorway).
'lit' going around 'mi' is 'LIMIT'.
(Other definitions for limit that I've seen before include "end" , "Boundary, demarcation line" , "Furthest point" , "maximum number" , "qualify?" .)