Before this time in the past (6)
I believe the answer is:
erenow
'in the past' is the definition.
(I've seen this in another clue)
'before this time' is the wordplay.
'before' becomes 'ere' (poetic term for 'before').
'this time' becomes 'now' (now is a kind of time).
'ere'+'now'='ERENOW'
(Other definitions for erenow that I've seen before include "Before this time (arch.)" , "Hitherto" , "previously" , "Before this time (poet.)" , "Before the present" .)