Cool vision for childhood (7)
I believe the answer is:
infancy
'for childhood' is the definition.
(I've seen this before)
'cool vision' is the wordplay.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'vision' becomes 'fancy' (fancy is a kind of vision).
'in'+'fancy'='INFANCY'
(Other definitions for infancy that I've seen before include "youth" , "beginning" , "First stage of life" , "minority" , "Early stage of development" .)