Train dog with ducks for weeks (4-4)
I believe the answer is:
choo-choo
'train' is the definition.
(I've seen this before)
'dog with ducks for weeks' is the wordplay.
I cannot really understand how this works, but
'ducks' could be 'oo' (OO resembles two zeroes or 'ducks' in cricket) and 'oo' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for choo-choo that I've seen before include "Child's word for train" , "Chattanooga train?" , "(Childish) train" , "Baby train?" , "A child's train, sounds repetitive" .)