Long ago, in the past (4)
I believe the answer is:
erst
I believe this clue is a double definition.
'long ago' is the first definition.
(archaic term for formerly or long ago)
'in the past' is the second definition.
(I've seen this before)
(Other definitions for erst that I've seen before include "Rest turned formerly" , "At first; formerly" , "in the past" , "in former times" .)