Document needed for father's pleasure? (8)
I believe the answer is:
passport
'document' is the definition.
(I know that passport is a type of instrument)
'father's pleasure?' is the wordplay.
'father's' becomes 'pa's' (pa can mean dad or father).
'pleasure?' becomes 'sport' (I can't justify this - if you can you should believe this answer much more).
'pas'+'sport'='PASSPORT'
'needed for' acts as a link.
Can you help me to learn more?
(Other definitions for passport that I've seen before include "Travel doc" , "papers" , "Travel authorisation" , "Travel ID" , "This ensures admission" .)