I tend to think about northern childhood (7)
I believe the answer is:
infancy
'childhood' is the definition.
(thesaurus)
'i tend to think about northern' is the wordplay.
'tend to think' becomes 'fancy'.
'about' says to put letters next to each other.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'fancy' put after 'n' is 'nfancy'.
'i'+'nfancy'='INFANCY'
(Other definitions for infancy that I've seen before include "youth" , "Early years" , "First stage of life" , "Early stage of development" , "Babyhood" .)