Identification of aggressive man resulted in retreat (8)
I believe the answer is:
username
'identification' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'aggressive man resulted in retreat' is the wordplay.
'in' indicates a hidden word.
'retreat' says the letters should be written backwards.
'emanresu' is hidden in the letters of 'aggressive man resulted'.
'emanresu' reversed gives 'USERNAME'.
'of' is the link.
Can you help me to learn more?
(Other definitions for username that I've seen before include "One's identifier on a computer" , "Log in identifier" , "Electronic identity" , "Person's computer ID" , "Online identity" .)