Hobby for dad? Stamp collector? (8)
I believe the answer is:
passport
'stamp collector?' is the definition.
(passports get stamped)
'hobby for dad?' is the wordplay.
'hobby' becomes 'sport'.
'for' means one lot of letters go next to another (I've seen this in other clues).
'dad?' becomes 'pas' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sport' after 'pas' is 'PASSPORT'.
Can you help me to learn more?
(Other definitions for passport that I've seen before include "one admits" , "Carte blanche" , "Document facilitating travel" , "Traveller's ID" , "you might need Visa with this" .)