Permit to overtake on the left (8)
I believe the answer is:
passport
'permit' is the definition.
(thesaurus)
'overtake on the left' is the wordplay.
'overtake' becomes 'pass' ('pass' can be a synonym of 'overtake').
'on' means one lot of letters go next to another.
'the left' becomes 'port' (left side of a ship - opposite of starboard**).
'pass'+'port'='PASSPORT'
'to' acts as a link.
(Other definitions for passport that I've seen before include "Travel identification" , "Traveller's aid" , "Document facilitating travel" , "International identification document" , "Traveller's ID" .)