Key from old man's Golf, say (8)
I believe the answer is:
passport
'key' is the definition.
(both can mean a means of accessing something)
'old man's golf say' is the wordplay.
'old man's' becomes 'pa's' (both can mean father).
'golf say' becomes 'sport' (golf is a kind of sport).
'pas'+'sport'='PASSPORT'
'from' is the link.
(Other definitions for passport that I've seen before include "Official document required for foreign travel" , "Document facilitating travel" , "Travel ID" , "Traveller's aid" , "entry permit?" .)