Ruler’s uncontrolled anger beheaded men (7)
I believe the answer is:
emperor
'ruler's' is the definition.
(emperor is a kind of ruler)
'uncontrolled anger beheaded men' is the wordplay.
'uncontrolled anger' becomes 'temper' (I've seen this before).
'beheaded' means to remove the first letter (the head of the word is removed).
'men' becomes 'OR' (military abbreviation for Other Ranks).
'temper' with its initial letter taken away is 'emper'.
'emper'+'or'='EMPEROR'
(Other definitions for emperor that I've seen before include "He rules over several states" , "Roman leader" , "Say, Nero" , "Ruler of large territory" , "A moth; a penguin" .)