Perhaps male ruler backing Persian king (6)
I believe the answer is:
xerxes
'persian king' is the definition.
(I've seen this before)
'perhaps male ruler backing' is the wordplay.
'perhaps male' becomes 'sex'.
'ruler' becomes 'rex' (I've seen this before).
'backing' says the letters should be written in reverse.
'sex'+'rex'='sexrex'
'sexrex' reversed gives 'XERXES'.
(Other definitions for xerxes that I've seen before include "King of Persia, son of Darius" , "Persian 14" , "------I, son of Darius I, attempted invader of Greece, 480-79 BC" , "Ancient Persian king" , "Name of two Persian kings" .)