Child with nearly everything is perfect (5)
I believe the answer is:
total
'is perfect' is the definition.
(I've seen this in another clue)
'child with nearly everything' is the wordplay.
'child' becomes 'tot' (term for a young child).
'with' says to put letters next to each other.
'nearly' means to remove the last letter.
'everything' becomes 'all' (all things).
'all' with its last letter removed is 'al'.
'tot'+'al'='TOTAL'
(Other definitions for total that I've seen before include "Whole, complete" , "Everything added together" , "final answer" , "Aggregate amount" , "Count" .)