Boy and not adult male (6)
I believe the answer is:
norman
'boy' is the definition.
'and not adult male' is the wordplay.
'and not' becomes 'nor' ('nor' means 'and also not').
'adult male' becomes 'man' (synonyms).
'nor'+'man'='NORMAN'
(Other definitions for norman that I've seen before include "1066 invader" , "British comedian, once a cult figure in Albania, d. 2010" , "- Mailer, US author" , "Ten sixty six invader" , "Australian golfer" .)