Troublesome tot to munch meagrely (6)
I believe the answer is:
pickle
'troublesome tot' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for pickle that I've seen before include "A preserve or an informal predicament" , "Preserved vegetable of informal plight" , "Marinate" , "tight spot" , "imp" .)