Be discriminatory perhaps, having lost the head (5)
I believe the answer is:
exist
'be' is the definition.
(I know that be can be written as exist)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for exist that I've seen before include "Have objective reality" , "Scrape by" , "Get a life!" , "Be alive" , "Have being or continue living" .)