We are - or used to be (4)
I believe the answer is:
were
I believe this is a double definition.
'we are' is the first definition.
(contraction of 'we are')
'used to be' is the second definition.
(eg 'you were...' means 'you used to be...')
'or' is the link.
(Other definitions for were that I've seen before include "SECOND PART OF 9" , "Used to be" , "'Are, in the past (4)'" , "Lycanthrope" , "SECOND PART OF 14" .)