Official document showing father's recreation? (8)
I believe the answer is:
passport
'official document' is the definition.
(passport is a kind of official document)
'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'
'showing' acts as a link.
(Other definitions for passport that I've seen before include "Travel doc" , "It could be important on holiday" , "This ensures admission" , "Travel authorisation" , "Document facilitating travel" .)