Young child in first half of Disney film (6)
I believe the answer is:
infant
'young child' is the definition.
(I've seen this before)
'in first half of disney film' is the wordplay.
'first half of' means to take half the letters.
'disney film' becomes 'fantasia' (1940 film).
'fantasia' halved is 'fant'.
'in'+'fant'='INFANT'
(Other definitions for infant that I've seen before include "Rudimentary" , "Small baby" , "Wee one" , "Small boy" , "Juvenile" .)