Maybe Thomas the Tank Engine munches on the track (4-4)
I believe the answer is:
choo-choo
'track' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for choo-choo that I've seen before include "A baby's train" , "A child's train, sounds repetitive" , "Child's railway train" , "Baby train?" , "(Childish) train" .)