1939 movie dog (4)
I believe the answer is:
'1939 movie dog' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for toto that I've seen before include "member of the 5d band" , "Dorothy's dog in The Wizard of Oz" , "[FRIEND OF DOROTHY]" , "Famous film dog" .)