Heroic animal runs home to young Belgian adventurer (3,3,3)
I believe the answer is:
rin tin tin
'heroic animal' is the definition.
'runs home to young belgian adventurer' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'home' becomes 'in' ('he's home' can mean 'he's in').
'to young belgian adventurer' becomes 'tintin'.
'r'+'in'+'tintin'='RIN TIN TIN'
(Other definitions for rin tin tin that I've seen before include "Dog Star" , "Canine star of many films" , "shot dog" , "Fabled canine" .)