Be in a different era (3)
I believe the answer is:
are
'be' is the definition.
(I've seen this in another clue)
'different era' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'era' is an anagram of 'ARE'.
'in a' acts as a link.
(Other definitions for are that I've seen before include "live" , "Is, in the plural" , "is for more than one" , "Unit of land measure equal to 100 square metres" , "(They/you/we) exist" .)