Exist as a career necessity (3)
I believe the answer is:
are
'exist' is the definition.
('they exist' means 'they are')
'a career necessity' is the wordplay.
'ARE' is hidden within the letters.
However, I'm unsure how this is indicated.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for are that I've seen before include "is for more than one" , "Exist; square measure" , "Is, in the plural" , "(We/you/they) exist" , "Era (anag.)" .)