Popular conception of earliest times? (7)
I believe the answer is:
infancy
I believe this clue is a double definition.
'popular conception' is the first definition.
'earliest times?' is the second definition.
'of' is the link.
(Other definitions for infancy that I've seen before include "Babyhood" , "Early stage of development" , "youth" , "Early years" , "Early stages of" .)