A boy's boy? (8)
I believe the answer is:
grandson
'a boy's boy?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'boy's boy?' is the wordplay.
'boy's' becomes 'grand' (I can't explain this - if you can you should give a lot more credence to this answer).
'boy?' becomes 'Son' ('son' can be a synonym of 'boy').
'grand'+'son'='GRANDSON'
(Other definitions for grandson that I've seen before include "Junior relative" , "Young male descendant" , "Male child of one's child" , "Dons rang (anag) - relative" , "Daughter's boy" .)