Life story, briefly (3)
I believe the answer is:
bio
'life story briefly' is the definition.
(short for biography; 'briefly' asks for an abbreviation)
This is all the clue.
(Other definitions for bio that I've seen before include "A life's work" , "Life story (abbr)" , "brief history" , "Prefix denotes life" , "Prefix denotes living things" .)