Used to be among the lower echelons (4)
I believe the answer is:
were
'used to be' is the definition.
(eg 'you were...' means 'you used to be...')
'among the lower echelons' is the wordplay.
'among' indicates a hidden word.
'WERE' can be found hidden inside 'lower echelons'.
(Other definitions for were that I've seen before include "(You/we/they) existed" , "SECOND PART OF 14" , "SECOND PART OF 9" , "Lycanthrope" , "(We/you) existed" .)