Tyke on a trike (3)
I believe the answer is:
tot
'tyke on a trike' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tot that I've seen before include "Add the little child?" , "Add; young child" , "Aggregate for infant" , "Rum measure" , "Palindrome for small child" .)