One murders macho monarch (7)
I believe the answer is:
butcher
'one murders macho monarch' is the definition.
I can't tell whether this defines the answer.
'macho monarch' is the wordplay.
'macho' becomes 'butch' (synonyms).
'monarch' becomes 'ER' (abbreviation for Elizabeth Regina, British Queen).
'butch'+'er'='BUTCHER'
Can you help me to learn more?
(Other definitions for butcher that I've seen before include "Meat seller" , "more macho" , "Slaughter" , "Kill brutally" , "Meat purveyor" .)