State the ruling head may be male (5)
I believe the answer is:
realm
'state' is the definition.
(realm is a kind of state)
'the ruling head may be male' is the wordplay.
'head' says to take the initial letters.
'may be' is an anagram indicator.
The initial letter of 'ruling' is 'r'.
'male' with letters rearranged gives 'ealm'.
'r'+'ealm'='REALM'
(Other definitions for realm that I've seen before include "World" , "the UK, perhaps" , "Kingdom; field of interest" , "Area of interest/activity" , "where ruler holds sway?" .)