Genuine male domain (5)
I believe the answer is:
realm
'domain' is the definition.
(I've seen this before)
'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 "Dominion" , "department" , "Monarchy" , "monarch's responsibility" , "Kingdom's" .)