Genuine male territory (5)
I believe the answer is:
realm
'territory' is the definition.
(thesaurus)
'genuine male' is the wordplay.
'genuine' becomes 'real' ('real' is associated in meaning with 'genuine').
'male' becomes 'm' (common abbreviation).
'real'+'m'='REALM'
(Other definitions for realm that I've seen before include "A Nation" , "region" , "Kingdom, or field of activity" , "World" , "Knowledge base" .)