Childhood in the imagination? (7)
I believe the answer is:
infancy
'childhood' is the definition.
(I've seen this before)
'in the imagination?' is the wordplay.
'the imagination?' becomes 'fancy' (fancy is a kind of imagination).
'in'+'fancy'='INFANCY'
(Other definitions for infancy that I've seen before include "youth" , "First stage of life" , "Early stage of development" , "Early stages of" , "State of early childhood" .)