Boy who never finishes playing? (5)
I believe the answer is:
gamin
'boy' is the definition.
(thesaurus)
'never finishes playing?' is the wordplay.
'never finishes' becomes 'gam' (I can't explain this - if you can you should believe this answer much more).
'playing?' becomes 'in'.
'gam'+'in'='GAMIN'
'who' is the link.
Can you help me to learn more?
(Other definitions for gamin that I've seen before include "Little devil" , "stray" , "Ragged child" , "Waif" , "Street urchin or impudent child" .)