Very much forgetting day in the remote past (5)
I believe the answer is:
early
'in the remote past' is the definition.
(in the early days)
'very much forgetting day' is the wordplay.
'very much' becomes 'dearly' (eg to pay dearly is to pay very much).
'forgetting' is a deletion indicator.
'day' becomes 'd' (abbreviation for day).
'dearly' with 'd' taken out is 'EARLY'.
(Other definitions for early that I've seen before include "Before appointed time" , "sooner than expected" , "before anyone else?" , "Prematurely" , "Post this for Christmas?" .)