Permit father's recreation (8)
I believe the answer is:
passport
'permit' is the definition.
(thesaurus)
'father's recreation' is the wordplay.
'father's' becomes 'pas' (pa is a kind of father).
'recreation' becomes 'sport' (sport is a kind of recreation).
'pas'+'sport'='PASSPORT'
(Other definitions for passport that I've seen before include "entry permit?" , "is the open sesame" , "This ensures admission" , "Travel ID" , "Travel identification" .)