Child beginning to trust stranger crossing line (7)
I believe the answer is:
toddler
'child' is the definition.
(toddler is a kind of child)
'beginning to trust stranger crossing line' is the wordplay.
'beginning to' suggests taking the first letters.
'stranger' becomes 'odder' (I've seen this before).
'crossing' means one lot of letters goes inside another.
'line' becomes 'l'.
The initial letter of 'trust' is 't'.
'odder' enclosing 'l' is 'oddler'.
't'+'oddler'='TODDLER'
(Other definitions for toddler that I've seen before include "Lord Ted (anag)" , "youngster" , "Child starting to walk" , "Feeble walker" , "Child just walking" .)