Tag large murder victim (5)
I believe the answer is:
label
'tag' is the definition.
(I know that tag is a more specific form of be known as)
'large murder victim' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'murder victim' becomes 'abel' (Biblical character).
'l'+'abel'='LABEL'
(Other definitions for label that I've seen before include "Descriptive tag" , "Tag, tab" , "Mark" , "Designate" , "Classifying name" .)