Permit drink after exam success (8)
I believe the answer is:
passport
'permit' is the definition.
(thesaurus)
'drink after exam success' is the wordplay.
'drink' becomes 'port' (port is a kind of drink).
'after' is a charade indicator (letters next to each other).
'exam success' becomes 'pass' (I've seen this before).
'port' put after 'pass' is 'PASSPORT'.
(Other definitions for passport that I've seen before include "Travel doc" , "the key to success?" , "Traveller's aid" , "Traveller's ID" , "papers" .)