Born in a bygone era (3)
I believe the answer is:
nee
'born' is the definition.
('nee' is 'born' in French)
'in a bygone era' is the wordplay.
'in' says the answer is hidden in the clue.
'NEE' is hidden in the letters of 'bygone era'.
(Other definitions for nee that I've seen before include "Born (to indicate maiden name)" , "Born as (French)" , "Prefix denoting woman's unmarried name" , "called before wedding?" , "Prefix indicating maiden name before marriage" .)