Beatles number maybe overly extended in the past (10)
I believe the answer is:
yesteryear
'in the past' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for yesteryear that I've seen before include "Time disappeared" , "Twelve months ago" , "The recent past" , "nostalgic time, perhaps" , "Period 14 [CENTENARIAN] lived through" .)