Young child initially timid with stranger, about fifty (7)
I believe the answer is:
toddler
'young child' is the definition.
(I've seen this before)
'initially timid with stranger about fifty' is the wordplay.
'initially timid' becomes 't' (I am not sure about this - if you are sure you should believe this answer much more).
'with' is a charade indicator (letters next to each other).
'stranger' becomes 'odder' (I've seen this before).
'about' indicates putting letters inside.
'fifty' becomes 'l' (roman numeral).
'odder' going around 'l' is 'oddler'.
't'+'oddler'='TODDLER'
Can you help me to learn more?
(Other definitions for toddler that I've seen before include "One taking first steps" , "Infant" , "One beginning to walk" , "Child just learning to walk" , "Child just walking" .)