Fame not all children possess (6)
I believe the answer is:
renown
'fame' is the definition.
(I know that fame can be written as renown)
'not all children possess' is the wordplay.
'not all children' becomes 'ren' (I can't explain this - if you can you should give a lot more credence to this answer).
'possess' becomes 'own' (synonyms).
'ren'+'own'='RENOWN'
Can you help me to learn more?
(Other definitions for renown that I've seen before include "Fame and public acclamation" , "Fame and distinction" , "High repute" , "Celebrity, fame" , "Fame, respect" .)